The plan is to get rid of white people. The more you get people to move away from traditional relationships the fewer kids they will have. Notice how lgbt self-identification only increases by any significant amount in majority white countries.

If you ask lefties on why this percentage goes up, the answer is "Because it's more acceptable now." Personally I believe that it is the indoctrination. It's considered cool to be lgbt these days, so especially younger people will be draw towards it.