Tom Wilson isn't picking on weaker opponents and it's not fear stopping him from certain fights. The problem I have with Wilson is the way he picks and chooses fights, it's always on his grounds. He'll chase a guy for throwing a big hit on his teammate, but ignores requests if it's from a hit that he threw. I really hate this type of mentality of only fighting when you're in the mood.
I always get the impression from Wilson that he thinks he's a big shot and everyone needs to get in line on their knees if they want an audience with him. He disappeared in the game after Gudbranson challenged him earlier this weak, but not out of fear. He wanted to de-escalate the situation, because he wasn't in the mood for a big fight and didn't think it was worth being targeted. Since the playoffs his ego has been greatly inflated to the point where he thinks he can goon it up, but is too good of a player to have to deal with lower class goons.