I think people are exaggerating the racism of Terra Formars (I joke about it a lot, because I think it's jokes) when it's really more classic Japanese xenophobia paired with the lack of cultural understanding of the west. Race relations are completely different in the east compared to the west, and that fukks with your head because you look at a show like Terra Formars with a western mindset, one in which institutional racism is ingrained, with a long history of mocking/stereotyping black people in media. But Japanese people don't really have any experience with that, so to them, a big black caveman-acting creature that's preying on (almost exclusively) white people doesn't carry the same subtext as it does for us westerners.
We see racism because we recognize elements of how black people used to be (and in some ways, still are) portrayed in media. Same goes for the German guy called Adolf. Sure, Japan was in WWII, but do you think that outside of some very forced (and rather weak) alliance with Germany, they gave a shyt about the European theater of war? Of course they know about Hitler and shyt but to them the things that happened in Europe are about as irrelevant to them as the Pacific Ocean is to us. Can you name the Japanese emperor of the top of your head? Outside of Pearl Harbor and stuff that's been a part of movies (like Iwo Jima) what do you really know about what happened over there. To keep it short, even if they know about all the shyt Hitler has done, his legacy doesn't carry the same weight in Japan as it does in the western world, which is why the name Adolf is less of a taboo.
Basically, Terra Formars is a series that really emphasizes how separated the western and eastern world still are culturally. Remember, this is what Japanese people think black people sound like:
They simply don't understand because they don't know.