It's not about tolerance. It's about recruitment.
It's not just about recruitment. It's also about deliberately shredding (what's left of) the moral fabric that binds our society together.
If you destroy marriage (through acceptance of "shacking up", rampant divorce, and homosexual "marriage") then you destroy the family unit. If you destroy the family, then socialist government can step in to the void as the surrogate caregiver. Total socialist-fascism or communism is then an easy next step.
This is why the Left is pushing the homosexual agenda so hard. Homosexuals are simply another tool used by Leftists to attack America in their war against our Constitutional republic.