Whether or not he is being rude depends on your interpretation of his intentions based on assumptions about how the performer will react.
Are you implying those people are auditioning ironically and know they are bad singers?
It does not seem rude to me to try and change the course of someone's life who is _drastically_ underperforming.
Is the definition of rude hurting someone's feelings? That doesn't follow the implication that rudeness shouldn't happen; sometimes people need their feelings hurt to inspire positive change.
Are you implying those people are auditioning ironically and know they are bad singers? - No. I have absolutely no idea why you ask that.
It does not seem rude to me to try and change the course of someone's life who is _drastically_ underperforming. - Leaving aside what underperforming could mean - so, if he means well, it's just not possible for Cowell to be rude, no matter what he says? I think that's just not what the word means to people (apart from you).
That doesn't follow the implication that rudeness shouldn't happen; - I can't parse that, sorry.
Are you implying those people are auditioning ironically and know they are bad singers?
It does not seem rude to me to try and change the course of someone's life who is _drastically_ underperforming.
Is the definition of rude hurting someone's feelings? That doesn't follow the implication that rudeness shouldn't happen; sometimes people need their feelings hurt to inspire positive change.