Without getting into the entire theme of your post, I just wanted to point out that, according the the FBI, Blacks account for about the same percentage of spree killers as they do in the population as a whole. So your claim that it's "mostly just young white males", while technically correct could be a little misleading. Whites make up the majority of the population in the USA, so they tend to make up the majority of most samples.
How common are African-American mass shooters?