Mike has Asian pride the way Kurt has gay pride. This idea is not original to me, but it made sense to me. Tina uses the stereotypes here and there to get what she wants, like scaring Principal Figgins in "Theatricality" and speaking up as "Asian Persuasion" in "Dynamic Duets." She expected a couple of things from Artie in "The New Rachel." She expected to be named the new Rachel. Callie pointed out that Rachel couldn't actually assure that for Tina. Tina also expected Artie to speak up when Kitty said something racist -- her "white chrysanthemums" line -- and he didn't.
Others have said that Artie wouldn't pick a woman to front for him, that he wanted a frontman. Tina confronted Artie about his sexism in "The Power of Madonna," and some of it took, but Artie's still got some sexism. Artie's a great admirer of Blaine's. Artie doesn't seem to have much homophobia left, and Blaine doesn't trigger it the same way Kurt did. Blaine's male and light-skinned, and basically in the consensual reality that Artie's in, unlike Brittany, who Artie believes is in her own magical world. The way Blaine does gender doesn't seem to bother any of the people at McKinley.
Blaine wants to make people happy, and he's got good manners. He blends in more by other characters' perceptions of him than by him really trying to blend in, although there's probably a mix there. Blaine doesn't want to pass, and outs himself whenever he feels it's needed, but he passes anyway. Viewers were shown pretty early on that he has a lot of the same interests that Kurt does, but he has other interests that are considered more typically masculine. He's considered one of the bros, and likes hanging out with other boys.
So there are a lot of reasons even aside from what a good performer he is that Artie would pick him as the new Rachel, and Artie's frontman. Blaine has really been pretty polite about it.
Tina has a lot of reasons for being angry. She knows who in ND -- and the school in general -- is sexist and racist. She's speaking up more and more, and she seems to have concluded that being polite didn't get her anywhere. I'm curious to see where that goes. I think it will keep building for a while.