All people are doing (and theres only a couple) are pointing out facts. They didnt play this and this song, they were sloppy here etc. It's called reviewing how the show was for you. Expressing your opinion of the show. I don't see anyone saying "metallica were shit, metallica suck" etc.
You're saying we should have 20 posts in a row saying "Metallica rocked, im so happy they came, i have no criticisms at all about the show" yay how boring.
It seems like there is alot of whinging because for every "whinge" there are 5 ppl that have to whinge about the person whinging, quoting their whinge, turning it into a big thing over nothing.