Its an old tactic. Go after the groups you get the most buy in to oppress, hatemonger, disenfranchise, etc and normalize changes to civil rights for these groups to normalize it in the mind of the public. Then you expand it slowly out to other groups.
Gays and trannies are these targets because regardless of color , there is religious reasons why people would be against them and also socially these individuals and the acts they engage in are detested by large segments of the population.
If you want to eventually maybe make it legal for a business to discriminate and refuse service to particular groups, test the public's tolerance of the policy on the gays and trannies first. If they don't really make a stink and even support it, then maybe you can apply the same to certain groups like black folks. This is the strategy and again, its not new. Overton window shifting basically.