The 'Can you do any better?' response to criticism is, and has always been meaningless.
In this instance, Harry Hill satirises current TV and he does it very well, as hi viewing figures and Bafta Award concur.
I fail to see why what he said was in poor taste. PSTOA is an entertinment show, and therfore fair game for Mr Hill's attention. To criticise, or in this case to gently lampoon, never makes any suggstion that the critic can do better - and Mr Hill would not suggest that he can sing at all. But no critic is suggesting that they have a superior talent for that on which they opine - so I am sorry to read that you are offended - but taste - like comedy - or singing, is a moveable feast. You will have to find something esle to watch instead.