That's more a human flaw than a referee flaw - I think we'd all do it to some extent, we just hope referees can rise above it. But keep in mind, Foster is officiating in the finals for a reason. He grades out as one of the best referees year in, year out. IOW, the league agrees with his calls at a higher level than the other refs.
The issue the players have with Foster is that he won't discuss why the call was made, and if you go on too long about it he'll T you up. So really, that's the calls against them that they influence, the technicals.
To be clear, I'm not a Foster fan. I'd rather he not officiate our games. But I think he's pretty consistent and the players should know where his line is. He's more old school than many of the others so you know he'll allow a lot of contact, and you can't overreact when you don't get the call you want (and probably deserve).