Depends on how much you like yourself. We all have traits we dislike in ourselves, and tend to react poorly to the people who display those traits in ourselves that we dislike the most. I find it completely believable that Riker would not get along with himself. Thomas sees Will as a failure, not having achieved a captaincy yet. Will sees Thomas as a young, inexperienced officer chomping at the bit to climb the ranks, without regard for safety or politics. Naturally they wouldn't get along.