There's no way the Legion would bring harm to nonhuman sentients. I mean, Gates himself was held illegally by the government when Ra's Al Ghul was posing as President McCaulley.

AND tortured. The Legion were the ones that exposed it and rescued them.

I'll admit that it's a weird coincidence but we don't know what's bringing them to our universe so if it's something sentient, it may have some kind of biases.

But the Legion would NEVER harm nonhumanoid sentients.