To answer my own question, here is my best guess about this sort of “groomer” logic.
IF you believe that attraction and orientation is a choice, and not something we are born into,
THEN you believe that “normalizing” gays in society will in turn influence more kids to make that choice, and therefore more kids will lead a sinful lifestyle and turn their backs on God. This is the only possible way I can imagine people calling homosexuals “groomers”, and it’s pretty despicable.
A purely religious amber frame, of course, and a set of anti-gay tactics we haven’t really seen since the early 1980s, which attempted to portray all homosexuals as perverse, sinful, pedophilic deviants who want to corrupt your children.
Also:
IF you believe that homosexuality is purely about what you do with your genitals, and not about who you love,
THEN you believe that there is no way to talk about homosexuality without teaching kids all the different things they can do with their genitals.
So again, I present this as a fair compromise:
All kids get taught about all “protected classes”, and as they mature, the conditions that require protecting in the first place. This education begins with the basics in kindergarten — be kind to everyone, period. Then, in first through third grade, we learn to extend that kindness to different types of people. Kids are very good at this naturally. My daughter has brought home books with gay characters, trans characters, etc., and doesn’t bat an eye. She often prefers to get dolls with dark skin, because “I think their skin is pretty”. She’s a good kid.
At the same time, we agree not to teach kids at these ages anything about genitals, sexual positions, etc. Proper sexual education can begin in 4th grade, and then in 6th grade they can show the same horrible slideshow to them with pictures of genitals mutilated by STDs. An effective curriculum!