That "x" person is lipsyncing. Also that "x" person sounds bad live but maybe that's because I'm comparing him/her with the average person instead of comparing him/her to Adele, P!nk or Christina, some of the best vocalists ever.
I don't notice that everyone hates someone until I'm directly told that everyone hates them.
It used to happen to me in high school, it's happened to me in Uni and it happened to me the other day at work. Everyone at work was like "...you do realise EVERYONE hates him (our boss), right?" and I was like "oh wtf, seriously Why?"