Why should he? It sounds like a lot of his income comes from home schooling families. But he does clearly think there is an association between home schooling and homosexuality, despite lack of a little thing called evidence. Thus a bash, and an unfair one, can be fairly inferred.
The causes of homosexuality are poorly understood. Boys with a greater number of older brothers do have substantially more likelihood of being gay. It has been argued that this proves a genetic cause, and it has been argued that this proves an environmental cause. I would argue that it proves that the cause of homosexuality, especially male homosexuality, is poorly understood, at least by those of us for whom sin will not do as an answer.
Suppose you were an objective seeker after truth, whereever it might lead, who decided to dedicate your life for the next thirty years to understanding the causes of homosexuality. Truth is, you would find a heck of a difficult time getting a job. And nothing gets a professor in hot water faster than saying the wrong thing about the origins of homosexuality. So good researchers who have a family of their own to support stay away from this. Instead we have people like the man in the OP who talks with confidence when he should be most humble.