I may not agree with PE's original assessment of GF, but I defend his right to say it. Perhaps his use of the word "rubbish" was the real problem.

It's OK to say you don't like something, as that's just a subjective opinion that others can take or leave. But to use the word "rubbish" offends those who like whatever is is thus described, as it implies their taste is in some way lacking, or that you think your own taste is superior to theirs. Naturally this gets their backs up.

For example, PE says above that he thinks opera is rubbish. OK, I understand you simply mean that you don't like it, PE, but to apply the word rubbish to opera is an insult to opera lovers, even though you might not have meant it that way.

As I've grown older my tastes in music have grown wider and now include genres I hated as a youngster (opera being one of them). There are still some types of music I don't particularly like, or know little about, mainly the stuff my son used to listen to (club type music, rave, hip hop or whatever it was - I've no idea what it was called). I may not like it, but I don't consider it rubbish, I just don't know a lot about it and it doesn't immediately appeal to my tastes. But I'm prepared to believe that if I took the trouble to learn more about it I might possibly be able to appreciate it. Right now I can't really imagine that, but I once probably thought the same about opera.