Paul the Apostle has always been a controversial figure since the time he was very young. As a young man, he persecuted the small group of Jesus disciples that grew up after Jesus' death. He considered himself a "zealot" at that time, or one who does violence for the sake of God. Then he claims to have seen Jesus face to face after Jesus had died, and Jesus helped him realize how wrong he was and gave him a commission: to bring Gentiles to Jesus. That certainly didn't do much for his reputation, for either the Jews or the Jewish followers of Jesus.
Today, Paul isn't in much better shape. Sure, he's really honored by many, especially evangelical Protestant Christians, but anyone who isn't of that fold seem to consider Paul a real problem. He's been accused of creating Christianity, of stealing Jesus' religion away from him. Paul has been considered a misogynist, an anti-Semite, a religious hypocrite, a bigot, and many other nasty sounding things.
The biggest part of the problem with Paul isn't what he himself did or said, but how he has been interpreted over the years. Peter summarized it the best: "In them (Paul's letters) there are some things hard to understand that the ignorant and unstable distort to their own destruction, just as they do the other scriptures." (2Peter 3:1). The fact is, Paul is difficult to understand. Perhaps this is because Paul wasn't a really great writer-- I mean, sentences that go for ten or more verses? A good portion of the problem is because Paul was writing letters: thus, he was speaking to a particular context, and without that context some of his writings can be used for anything. And Paul occasionally uses some strong language, which need to be taken in their own context.
Paul himself was a pretty simple person, and his whole theology can be summed up in the experience he had with Jesus, which is described three times in the book of Acts and referred to in Galatians 1. There are two things that really shook Paul's thinking in that experience, that can summarize his entire approach to theology.
1. Jesus is Lord. What Paul realized, immediately, is that Jesus is a great spiritual power. This isn't the same as saying Jesus is God (although Paul might as well have said that in his statement on creation in Colossians 1), but that Jesus is worthy of being followed and obeyed and honored as king of creation.
2. Gentiles are accepted to be followers of Jesus. Because Jesus commanded Paul to go to the Gentiles to make disciples (which Paul refers to many times), his outlook on the gospel was different than most of the other followers of Jesus. He demanded that Gentile believers could have their own customs and traditions because they were not under Moses' law. He also demanded their equality in the Jesus synagogues that were popping up.
If this is Paul, he sounds more like a Christian civil rights leader than a bigot. And if he is pointing people to Jesus, then how can he be creating a new Christianity? This is because it isn't Paul, but people who use Paul who are the problem.
The problem began with Marcion, the first Christian heretic. His understanding of Paul's letters is that there were two gods: the Old Testament God and the New Testament God and that Jesus defeated the OT god. The idea of the OT presenting a "wrathful" God and the NT presenting a "merciful" God continues to this day. The fact is, all throughout the OT, God is presented as "compassionate, forgiving, slow to anger." The NT helps us realize that WE need to act that way as well.
Patriarchalists also make use of Paul. They take passages that seem to say that Paul is refusing women leadership in the church and to remain submissive (interpreted as "under their husband's thumbs") and ran with it. In doing this, they had to ignore all the women who Paul praised in the church's leadership (Romans 16, I Corinthians 16), and the fact that they didn't understand the context in which Paul wrote (in I Cor. 14:34 Paul is quoting a letter from the Corinthians, not presenting a personal view, which he strongly disagrees with immediately after).
Antinomians, who oppose the use of any law, also make use of Paul. Paul does oppose the specific use of Mosaic law to the Gentiles, but he certainly approves of many laws in the church, including sexual purity, no vengeance or violence, caring for the needy, and no greed, all in accordance with what Jesus teaches.
Anti-Semites have used Paul (and John) to speak against "the Jews". However, when Paul was speaking about "the Jews" in I and II Thessalonians in negative, even harsh, terms, he was speaking of a certain kind of Jewish person (of which he was himself). More accurately the term "Jew" in the NT should be translated "Judean", or one who holds to a Judea-centric form of Judaism. These are nationalists, who opposed and persecuted Paul because he was decentralizing Judaism.
Others, such as Augustine and Calvin, used Paul to create a new orthodoxy, and a new vision of God, who not only rules the universe, but has control over every single event. This is not the teaching of Paul, who claimed that God controlled certain aspects, but also recognized that God gave rule to human beings, who made their own decisions.
All this to say, we should allow Paul to speak on his own, within his own culture. Let's not put on Paul all the misunderstandings and mistakes of Christianity, simply because people want to use the ancient writings for their own purposes.