Indeed, though I'm not terribly confident that we hear equally much about everyone's justification. But regardless, if all the apparently racial-superiority-induced violence went away, white men would be among the least likely to commit mass shootings. But is that even it? To what extent are these manifestos just a rationalization for what is motivated by a feeling of hatred or despair that the shooter can't suppress, so they cast around for whatever seems the most plausible reason?
The bottom line, though, is that mass shootings are definitely a problem with men, and definitely a problem with the U.S., but mostly not a racially-associated-culture problem.