"They are fitting symbols then. But why is justice recruiting a Galra?"

Thace wouldn't call the Galra Empire just even by the most lax definition. Instead of order and stability, the empire brought only conquest and oppression. That is why the Blade of Marmora fight, but when outnumbered and sorely outgunned, one can't always hold to ideals to win. The things he's sometimes had to do to keep his cover weigh on his conscience.

He's not going to point that out, aside from the question though. Reminding a bieng that claims to be justice of his less than honorable and just actions is probably tantamount to suicide.