The west has never actually experienced communism so they just kinda look at it and go "Eh, you know this could work if we executed it correctly...", plus communism has always sounded better than fascism on paper.
@Daggerfella: All great points, I also have to add that the injection of Marxism into pop culture is another part of the issue of why it seems to be so accepted.
Remember when people used to wear a shirt with the face of a genocidal Marxist dictator?
https://en.wikipedia.org/wiki/Che_Guevara