Some of the strangest attacks on the Bible come from those claiming to be Christians. One example is the claim that Paul was not actually a follower of Christ, but rather a heretic and false teacher who contradicts the teachings of Jesus. Specific claims include: Paul was a deceiver who taught his own religion doctrine perverting the teachings of Jesus. Paul is the only one saying we're not under the Law; he says the Law does not matter. Paul is a false teacher mentioned in Revelation chapter 2. And so on and so forth.
In reality, Paul and Jesus strongly agree on their theology, as explained in Scripture. Contradiction between Paul and Jesus can be forcibly read into the text, but it not easily read out of it. Here, we'll use the specific claims above to frame a look at how Paul and Christ are clearly in agreement. Beyond that, we'll see how this position leads inevitably to a crisis over the inspiration of the majority of the New Testament.
Theologians have always noted thematic differences between Paul's letters and the Gospel narratives, but rarely have trouble harmonizing them. Jesus preached prior to His resurrection, Paul and the other apostles preached after. We would expect to see different aspects of Christian doctrine emphasized in each case. The apostles were countering heresies related to Christ, and explaining the applications of His ministry. There's nothing inherently wrong with Paul's writing being more theological or philosophical than the Gospels, which are more factual and historical.
Paul and Jesus consistently agree on all theological points, even those Paul's critics seem to get stuck on. Paul (Romans 5:1, Galatians 3:11) agrees with Jesus (John 5:24, Luke 18:9-13, Matthew 7:22-23) on faith-only justification. Paul (Romans 13:8-10) also agrees with Jesus (Matthew 19:18-19) that the Law is important. Paul (Romans 2:6) agrees with Christ (Matthew 16:27) on eternal rewards and punishments based on our behavior. Paul (1 Timothy 2:5, Colossians 2:9) claims Christ as both God and the exclusive Messiah, just as Jesus said of Himself (John 14:6, John 8:58).
Paul claimed his faith was based on what he himself was taught, in 1st Corinthians 15:1-11. This is acknowledged as the earliest dated depiction of Christian beliefs — originating just a few years after the resurrection. Paul's ministry was early enough for the other apostles to counter or refute him, in their own epistles and Gospels. He died early enough for the surviving church to freely label him a heretic, particularly in writings completed after his death. Yet, they do not.
Paul never says that the Law "does not matter". In fact, he notes the Law is what convicts us of sin (Romans 3:31, Romans 7:7-8, 12). Paul even used the Law as a way to witness to his fellow Jews about Christ (Acts 28:23). Both Jesus and Paul preached the importance of the Law, but applied it in a way which overturned the prevailing Judaic view. Jesus, in fact, was often criticized for "breaking" the Law, when He was actually living out the more Godly, appropriate fulfillment of it (Matthew 12:10, Mark 7:5, Mark 10:5, Luke 6:7-9).
Paul's attackers claim "no works salvation" means telling people they can sin as much as they want, and still be saved. This is sometimes called "easy believe-ism". However, Paul explicitly counters this idea (Romans 6:1-2, Romans 6:15-18). His letter to the Ephesians is a call to unify theology with lifestyle. Elsewhere, he clearly states that a changed heart leads to a changed life (Galatians 5:16-25), and condemns sinful lifestyles (1 Corinthians 6:18-20), even in those who don't have the formal Gospel (Romans 1:18-20).
Paul's critics suggest that some New Testament passages label him a false teacher, a claim similarly lacking in substance. One such method attempts to link 2 Timothy 1:15, Acts 21:27-21, and Revelation 2:2. In 2 Timothy, Paul notes a severe lack of support from the churches in Asia. In Acts 21, some Jewish people were angry about Paul's preaching in Jerusalem, and his association with a Greek from Ephesus. Revelation 2:2 commends the Ephesian church for rejecting false apostles.
Those attacking Paul claim these all add up to evidence that Paul was rejected as a false teacher, and that rejection was commended by Jesus. Beyond this interpretation not matching any other historical or scriptural evidence, it also reads far too much into the text which is just not there. That is, Revelation chapters 2 and 3 specifically name false teachers — but not Paul, who founded the church in Ephesus. John wrote Revelation well after Paul's death. So, if Paul is the grand heretic he's made out to be, that omission makes no sense. Depictions of heresy in Revelation cannot sensibly be applied to Paul.
Even beyond specific scriptures, attacking Paul as a heretic leads directly to an important question for those who reject his theology. Namely, are they willing to follow that to its logical conclusion? If Paul is completely heretical, those who approved of Paul's ministry can't be trusted in their theology, either (Psalm 101:7, Proverbs 13:5, 1 Thessalonians 2:4, Matthew 7:15). One cannot reject Paul's theology as aberrant while simultaneously accepting any books of the New Testament, other than Matthew, James and Jude. Consider the following:
• Luke clearly approved of Paul's message, since he chose to travel extensively with him on missionary journeys. So, critics of Paul should be skeptical of both the Gospel of Luke and the book of Acts.
• Hebrews may or may not have been written by Paul, but it constantly speaks of justification by faith and the movement from an Old Covenant (the Law) into a New Covenant. Someone calling Paul's teachings contrary to Christ presumably won't accept a book that could have been written by Paul himself.
• Peter commends Paul and his writings, even after Paul's death (2 Peter 3:14-18). So, Peter's writings would be theologically suspect.
• Following this, Paul's attackers should eliminate the Gospel of Mark, since it was recorded by an immediate disciple of Peter, if not dictated outright by Peter himself.
• Revelation encourages Ephesus, a church Paul founded and then stayed with for three years, to return to its "first love", to the way that church was in the past. It explicitly praises them for weeding out false teachers, mentioning several (Revelation 2:6, Revelation 2:14-15), yet makes no mention of Paul as one of them (Revelation 2:2-5). Paul preached extensively and successfully in the regions near the seven Churches, and died before John wrote most of his works. And yet, neither Paul nor his teachings are mentioned as heretical in any part of John's writing. So, John apparently had no problem with what Paul preached, making all of his writings questionable as well.
For those keeping track, the above affects every New Testament book but Matthew, James and Jude. All but three New Testament books were either written by Paul or by someone who did not object to his ministry when given a clear opportunity. And those three books don't mention Paul or his ministry at all. Virtually the entire New Testament was either written by Paul, or by someone who approved of his message. Rejecting him not only means rejecting most of the New Testament, but questioning the spiritual judgment of two of the original Apostles, John and Peter.
Those who condemn Paul as a false apostle, but accept books like Mark or Luke or Revelation are dealing in serious contradictions. In practice, I don't know many upbraiding Paul who actually follow through by rejecting all of the books "contaminated" by his theology.
Rejecting the writings of Paul is simply not Biblically justifiable. This does not prevent the anti-Pauline camp from being passionate, aggressive defenders of what they believe. Unfortunately, in my experience, most who reject Paul do so with an arrogant and hostile attitude. They rely heavily on repetition of arguments, all based on Scriptures which can be easily understood when read in context. Testing our faith is good, and necessary (Acts 17:11, 1 John 4:1), but reason is only useful when someone wants to be reasonable.
For that reason, I don't recommend spending a great deal of time debating the issue, should it come up. In particular, those who have made up their mind about Paul — at least in my experience — are highly unlikely to discuss it reasonably. It's good to have an answer for every possible argument (2 Corinthians 10:5), but not everyone is going to be receptive to what we say (Matthew 7:6). If all we do is make a reasonable case, then let the Holy Spirit take care of the rest (Mark 6:11), we've done enough.