In reality, twin studies and adoption studies have shown a large genetic component.

We don't even need twin studies to know this. It must be true unless you're a young-earth creationist. If there wasn't genetic variability in criminality, humans wouldn't have been capable of evolving to be so much less violent than other primates.

(And of course, disparities in male/female behavior is obviously biological.)

> I haven't studied the demographic data at length recently, but fairly sure that your assertion does not hold for high income blacks.

In fact, it does hold in higher income brackets too. And I'd bet whites are more violent than Asians after controlling for income, too.