Judging has nothing to do with opinion unless it concerns an immediate opinion about the corps' performance there and now. A past opinion should have absolutely NOTHING to do with a performance score. A judge cannot have a predisposed opinion about a corps if s/he wants to be considered impartial.
Your example: you may not like ES or Cru - the corps themselves - but if you were to judge a performance by one of those corps could you give them an honest score? Assume they were actually better than the Bucs on that given night - would the Bucs still win in your eyes? Would they still win on your sheets?
Whether you would be honest or not, there have been judges in the past that wouldn't be. One judge I remember from the early 90's made it very clear he hated the corps I was in, and we'd see multi-point drops in his caption whenever he judged. This judge had the (dis)honor of judging finals a few years ago, where my ex-corps came in 1st in his caption in prelims, but dropped to 4th in his caption in finals - a full 2.0 point drop from that judge alone.
Over the past few years I have loved watching the Renegades. They perform for the fun of it - for the fans - and really don't seem to care how they place as long as the fans loved the show. Kinda reminds me of Empire before winning took over. This year was a blast. I, personally, thought they had a better show on finals night. But I also loved the Hurcs as well. Actually, this was the first year in a while that I enjoyed just about everyone. I would have liked a better Renegades placement in finals, but I learned a long time ago that the placement matters much less than most make it out to be.
The only downside I saw this year were the rude Bucs fans around us at prelims. There is no doubt in my mind that the Bucs trounced everyone, but these people refused to enjoy any corps that wasn't Bucs, and specifically jeered ES for daring to be positioned 2nd to the Bucs on the way into prelims. Now that I live near Reading, I was actually embarrassed that these people are tied to my (now) hometown corps.