Kevin (not his real name) is a friend of mine at theological college. When we started, there were some people I naturally got on with very well, and Kevin wasn't one of them.
I guess the main problems I had were that Kevin was from quite a different sort of church background to me, and we talked a very different theological language. To me, what he said just sounded as if it was empty cliches and as if there wasn't much actually going on. When he spoke about his faith and some of his spiritual disciplines, it didn't sound true to me and to be honest, I really didn't see what he was doing at theological college.
It wasn't until we actually had to spend time together praising Jesus that I really recognised him as a brother in Christ, and all of a sudden, I found him much easier to love.
My plan now, when I find other people who claim to be Christians really difficult to love, is to ask them to tell me about Jesus, to try to see their passion for him.
Maybe that says more about me than about anything else. There's one local church leader, who I know only from a book of theirs which was badly thought through and unsound. My opinion of them is very low. But other people who know them know the good work they are apparently doing and love them better and are willing to put up with some less than amazing books.
There really isn't a substitute for knowing God together for learning to love someone.