Prah: Leftist is never bad unless you ask an upper class conservative person who cares more about his money than the people he employ for his multi-billion dollar business company. Also most satire is done by people who are leftists.
Treasure: Oh, I thought that leftism was as in left-ism, as in "faux left wing", as in somebody who pretends to belong to the so-called "left", only he really doesn't and plays it revolutionary from the comfort of his own couch... I guess the same word can have a different meaning for most people then. As for satire being done by leftists, well I guess, indeed the satirists satirize something without trying to change the situation they're satirizing -but I'd wish satirists came from more diverse environments really..
I think it may be that people often use the broad, sweeping terms in relation to the other lot, or to their (wider) lot in contrast with the other lot. Thus: over there are the leftists, whereas I (on the Right) am a conservative/liberal/libertarian/etc. Or: over there are the rightists, whereas I am a socialist/liberal/Judean People's Fronter/etc.