I don't quite get the hate for the Heat's "Big 2 and a half". It's not like they murdered somebody.
Slam, in the greater scheme of things, you are right.
However, this is the world of sports, where much emotion happens on a visceral level. Tribal loyalties rule the day and slights and indiscretions get magnified.
To answer your question:
1.The Decision,
2. the pretentious behavior at the Miami press conference anointing the new "big three" and predictions of the number of championships (haven't seen one yet),
3. "I don't foul out of games!",
4. ripping out Rondo's elbow intentionally to take him and us out of that series,
5. breaking Kobe's nose in an ALL-STAR GAME?!?!
6. hitting a Pacer (I forget who) from the side and knocking him down like an NFL cornerback, and not getting tossed for it,
7. etc., etc, etc,
It's as simple as this:
Nobody roots for Goliath.
And those who would normally be indifferent to Goliath when he's not bothering them, start to hate Goliath when he's all cocky and tells everyone how great he is.
This. I don't really buy the 1-7 argument in it's entirety. It's the idea of a super-team that no one wants to get behind. Ala this:

I think that what all of our responses point out is that many, many, many people dislike the cHeat for many, many reasons, not all the same, necessarily.