I don't feel too bad for those who obviously haven't prepared more than singing in the shower or dressing up wierd, but occasionally one or more of the judges will be in a pissy mood and just crap all over someone who actually has some talent and who has made an honest effort to be a professional singer, and I think that really reflects poorly on the judges. It's totally unprofessional behavior and I think those contestants, the ones who really do show up prepared, deserve a little courtesy.
The fact that they don't get it is why I watch the show to see the contestants and I pretty much ignore what the judges and hosts say. As Pooh says, it's an entertainment show and different people are entertained by different things. I am personally not entertained by people acting poorly or disrespectfully towards others who have earned, or made an honest effort to earn, some respect.
It's the same reason why I'll give 100% respect and professional courtesy to the worst student pilot I fly with even if he sucks and tries to kill me, as long as he's trying. If some guy shows up, sucks, doesn't try, hasn't prepared, or tries to displace blame for his lack of ability onto me, then he will not get any respect or courtesy from me beyond the bare minimum required by military regulations.
I try to follow those rules regardless of who the audience is, and it's frankly embarassing to watch the idol judges act so poorly towards certain constestants. But disrespectful behavior is the "in thing" right now in the US so the show producers are going to go with what works. Me, I'll watch it for the singing and ignore the judges because they quite often act in a manner that I consider to be shameful.