Ugh, those are total shit reasons, and sadly, very obviously true. But, isn't Damian half Southeast Asian? Of course his lineage is composed of villainy, which isn't a positive portrayal (well, I guess Dami isn't either...), but they ARE there, at least.

The annoying thing about the excuses I listed is that people still actually use them.  It's ridiculous. 

I think that's true about Damian, but I think the OP is saying that there is a scarcity of characters of that background, and that seems undeniably true.