Musical elitism, simply put, is the valuing of one's own musical tastes as the standard by which all music should be made, or the standard that all others should use to choose what music they listen to. Musical elitists will oftentimes use one of the following words in their tirades against their target band: shitty, sucks, lame, terrible, or any other standard derogatory terms. Musical elitism also comes bundled with musical stereotypes, i.e., all people who listen to Linkin Park are wangsty teens, all people who listen to Evanescence are goths, all people who listen to Avril Lavigne are posers, and so on.
Disliking a band for whatever reason does not automatically make you a musical elitist; the tag comes when one begins to put their standard against others and demand that they give up their "inferior" music for much more "sophisticated" tastes.
Everyone is free to enjoy whatever music they like, from Britney Spears to Nirvana to Tool to whatever underground band you may enjoy. People's tastes will differ endlessly and said tastes ought to be respected, whether or not you like the band they enjoy. Everyone is also free to criticize any band they wish, but when one begins to demean people for what they listen to, their integrity suffers, while their standing with other elitists rises.
2: Maybe because I enjoy listening to it?
1: That makes no sense. You are an idiot.