I must disagree strongly with whoever said "individualism"--most of the time individualism is a defiant response to those people who lust for power over others, and as I said, THAT (lust for power over others) is the real problem.
I am an individualist--I believe that since this is my only life (an "afterlife" is uncertain), NO ONE but me will dictate what I do with it. What is wrong with that? I don't believe I'm better than anyone else, just that, like everyone else, I have a right to self-determination. Most advances in human history were made by individual initiative--so stifling that initiative naturally serves to hold humanity back.
"Nationalism" (at least that which goes beyong normal, healthy concern for the well being of your homeland) in its more extreme forms is actually the opposite of individualism, as it advocates subjugating individuals to the state--thus again playing into the cynical hands of those who lust for power over others.
So why do some people hate people who assert themselves against people who wish to dominate them? THOSE people who oppose them are what is holding humanity back.
(BTW lust for power over others is NOT individualism, at least not the way I've heard the term used. Lust for power over others is megalomania, to varying degrees.)