I don't think that anyone said that Paul was anti-Christ. As I mentioned, Romans (and much more in the Bible) helped me through an especially tough time. I knew that some of Paul's teachings were different, however, and was just curious about how or why Christ's example was changed in at least some ways by "Christians"--even so soon--after He died. Obviously, many religious leaders have been aware of the differences. That does not mean that anyone who recognizes the differences is automatically throwing the baby out with the bath water.
Yes, we are all sinners. I know I am. However, the issue that I was referring to has to do with beliefs within each religion, denomination, church, etc. I think I am fairly open to the fact that there are a lot of different religious beliefs out there. However, I personally find it much easier to worship with and be part of a group whose beliefs are closest to my own--and match what the religion of my choice is to represent. Although we can learn from each other's differences and perhaps influence each other, we can also do that in the real world--outside of one's place of worship. To elaborate on your example about David, it seems to me that there is a big difference between David as a murderer (and yes, repenting and being forgiven later) worshiping in church with other Christians vs. a Christian leader condoning murder.
Of course, some churches (universalist?) are open to many kinds of beliefs, and that works well for people who want that. In some ways, I think I would rather be there than in a place that seems to stand for one thing--but then practices something else.
Different people obviously have different opinions about the Bible. What has been very helpful to me is to realize to whom each book was written, the "world" at the time, BUT how the we can apply the lessons to our own lives today--when read as a whole and using it is a guide and mirror. I admire those who have taken the time to learn more about how the Bible came to be, the content of the original language, and even what books men decided not to include.