There’s a big difference between being confident and standing up for oneself, though, and being inconsiderate and rude. Many people (of all races and genders) confuse the two.
Someone who says, “Excuse me, please don’t cut in line,” is standing up for themselves. Someone who replies, “Sorry, I’ll cut in line whenever i want to, deal with it,” is not standing up for themselves; they’re just being rude. But the latter will probably describe themselves favorably as “I’m someone who stands up for myself and I don’t care what others think.”