That may be true, but we should still avoid false equivalencies. There is scientific evidence for a casual relationship between testosterone and violence. Even if that is debated and there is no full consensus, there is still more evidence for it than there is for the idea that a person's race has a casual relationship on their propensity for violence all else being equal.
Your second statement doesn’t logically follow the first. It suggests that there is a similar claim of a cause for the statement that black people are more violent which is as strong (however weak and disputed) as the claim of this cause of testosterone.
Should be as much of a reason to doubt it and brand such statements as bigotry as “blacks are more violent”, no?