John Karalis of the Examiner (and Red's Army) has a nice look at the change in perception of Kevin Garnett. In short, KG has always been this way. Now that he has tasted success and gotten a lot more scrutiny, people are starting to turn on him.
For more than a decade in Minnesota, you were beloved. People marveled at your ability. People loved your intensity. People used your loyalty as an example. You had everything. Why else would someone stuck on mediocre teams in a small market become a marketing God? Your intense emotions on the court were tempered by an infectious smile and polite demeanor off the court. Perfect.
Then you came to Boston. And you didn't notice it right away, but that's when people started to tear you down. Sure, people were happy to see you get your ring, but some people suddenly started scratching their heads about you.
"Did KG really get down on all fours?"
"Does KG really need to yell like that?"
"Does KG shut up at all on the court?"
What has changed about Garnett? Nothing but his address, really.