KG is very private when it comes to his... by golly... private life. A lot of times, especially self-absorbed writers like Jim Gray, think it is their right to know, get, and write about anything they want. That was never sat well with KG. He's said hundreds of times that what he does while playing basketball is fair game, but when he's not "at work", don't expect him to talk about his personal stuff.
This kind of behavior only comes off as being a jerk to people that think it's responsibility to give them his time, all the time. There has always been a tiff between him and the media... hell, Lacie Banks, formerly of the Chicago Sun Times, wrote an article in 2004 admitting he voted Jermaine O'neal as MVP because he gave Banks a pregame interview, and KG wouldn't! That is the danger and power writers have... they can trash someone over spilled milk.
As fas as KG being a jerk to ball boys and equipment managers?? That's the first I've heard of this. In Minnesota it was written dozens of times that KG treats EVERYONE on the team equally, whether it be teammates, ball boys, equipment guys, or parking lot attendants. There were several stories written about his gift giving, and that nobody associated with the players was left off his list.
But I don't know him personally, so I can only go off what I hear and see and make my opinions from there. Maybe he's not the nicest guy in the world, but I'm pretty confident that anything negatives usually come from his unnatural passion to win. Anytime he sees something get in the way of that, I think he lets it be known that he doesn't like it.