First, the top of the article about how Paul might have been gay says:

In presenting this article, I am NOT saying that I, or any member of the Universal Fellowship of Metropolitan Community Churches, agrees or diagrees with it. I am presenting because it is interesting.

Second, just because the MCC doesn't think it's a sin doesn't mean that Paul didn't, either. It's one's own views on something that make it a sin to oneself, not the rest of society's, and certainly not those of a society that exists two thousand years later on a different continent.