It would be absurd to assert that all members of any race have a genetic predisposition to impulsivity, and the most basic reason is that most members of any race do not demonstrate chronically impulsive behavior. One assertion entails that most members of any race will not be chronically impulsive and thus not worrisome from a societal view, while the other entails being suspicious of every member of a particular race. C'mon, man!
Oodles of studies on twins indicate that impulsivity and criminal behavior are products of both environment and genetics. What isn't certain the is proportion for each. I have a list of studies, if you really want me to insert them, but I suspect you understand this.
Here's the basic question: how do explain the wide disparities in crime rates between racial groups? It's not just environment. Do you seriously believe that the reason Asians commit drastically lower crimes than whites, blacks, Hispanics is solely because of environmental factors? It's well-established that intelligence has an inverse relationship with impulsivity. Asians have a mean IQ of 108. Asian males also have, on average, less testosterone than males of other racial groups. Those variables have no bearing on the far lower crime rates among Asians compared to whites, blacks, Hispanics? None?
And going way back to something I mentioned originally: how do you explain the many, many families that have, for instance, two well-behaved, non-impulsive children, but then have a third who is impulsive and antisocial? In all those families, are the parents treating that one child differently than the others? Really? I realize most do not interact with kids on a daily basis, but few things become clearer over a teaching career than the fact that there is a subset of students whose impulsive behavior is not simply a matter poor parenting or abuse. You begin to have a little more forgiveness and patience once you recognize that. Particularly with the younger ones, some of them really do lack an ability to control this behavior.