People read way, way too much into what is said in interviews, in general. I agree about the self-confidence/positive reinforcement being a good thing and all that, but it's pretty meh overall.
EDIT : Blaze, I see you've mentioned Pietersen. Despite what I said above, I often criticize him on this issue a lot because his comments sometimes spill over to disrespect to the opposition (see the "pie-chucker" comments to Yuvraj and "selfish batsman" to Chanderpaul"), and he just doesn't appear like he puts the team above his personal interests at times... like the outrage at being dropped from ODIs after averaging <20 for 2 years, and the recent "we won the Ashes because I gave up the captaincy" comments.
In summary, I'd much rather the McGrath/Harbhajan/Ponting type ****iness over the Pietersen brand.
You see this is where there is a bit of taking things out of context, in the "we won the Ashes because I gave up the captaincy", which when I read the interview, I couldn't see what people were talking about and imo it was a bit of a hatchet job on KP, to make him look bad. If anything, he was talking up the job done by Flower and Strauss and suggested that if Moores and himself were still at the helm, they wouldn't have won, which is more than likely correct. Of course the press being the press, that wasn't interesting enough and stitched him up.
As far as the other comments, they are neither here or there and I'm sure if you look through the interviews of the people you mentioned, McGrath/Harbhajan/Ponting, you could find comments you don't like, especially during the course of a series.
All the interviews, I've ever seen of KP, he comes over as a decent bloke, who contrary to what people say, only ever talks about the good of the team and mainly has good things to say about the opposition. But obviously it's a choice who you perceive as arrogant and then take it step further and dislike because of one thing or another that someone has said.
I personally love to see a bit of ****iness and arrogance in sports men, there's nothing wrong having players around like that, at all and it would be a boring place if everyone acted the and played the same. Cricket needs big personalities and people who object to such people, imo are intimidated by them, which frankly is a bit sad.