The idea that males are naturally more inclined to aggression than females isn't controversial. There are exceptions, of course, but on the whole this is true.
What I translate that Walsh is talking about are large sample sizes here, not the granular, individual level. I believe it is very likely that male aggression would increase with the reduction of positive outlets for these natural tendencies.
There are also exceptions to the statement that straight people love football. There are homosexuals that love football and heterosexuals who do not, but on the whole I don't think it's absurd or stupid to believe that a higher percentage of heterosexuals enjoy football and a lower percentage of homosexuals do not.
What's absurd is that it should be eradicated because it something that Conservatives and homosexuals in larger numbers support. It isn't the data that are problem; it's the conclusions that some people make after observing the data that are stupid.
In animal science, it is understood that providing dogs with stimulating activities will reduce their naturally destructive tendencies. Those therapies, if you will, reduce the likelihood of bad behavior. It's not a stretch to believe that the same would occur to a population of males in America; it's certainly not absurd and stupid to come to that conclusion. Like a chew toy or a dog puzzle, football and other sanctioned sports can be a positive outlet for a natural phenomenon that left unfilled could otherwise lead to destruction.
