Wow, I guess I should stop using this word...
for me, "whatever" means "I don't care," but definitely not in a mean way. If my friend asks me what I want to do on a Friday night, I'll say "I don't know, whatever," but it doesn't mean that I don't care enough to give a response, it just means that I don't have an opinion and they can decide.
And I would never use "whatever" as an insult or in an argument...that's like surrendering, because my friends would just assume I'm not intelligent enough to think of a response, and then make fun of me because they won the argument!