Firstly, while you can now see who rated your project low, this doesn't mean said person hates you. They probably don't even remember doing it. Sure, mention it to them (I myself have sent a few choice PMs), but don't dwell on it. You have probably done it at some point, and would probably rather forget about it. See this as a chance to correct your mistakes and give older projects a fair rating if you want.
Having said this, I would hate to see people bullied into giving 5* ratings to everything for fear that they may get picked up on the odd 3.5* etc. As long as you express your honest opinion.
But seriously, ratings on this site are typically ridiculously skewed anyway, so I wouldn't get too hung up over it. Most people don't care about ratings at all.