I didn’t get that impression. You’re not wrong that something can be justified “for the children” but have an ulterior motive. But I think what’s being argued is that the initial motive is actually honestly for the children and that that goal blinds people to the reality of how bad or pointless or even perversely harmful the proposed solution is.

I think it's a mix of cynical PR campaigns and honest activism, and I'm not smart enough to say which is the biggest factor in each instance.

Separately, the honest activists are often lying to themselves, in the sense that their real motives are not what the they tell themselves and others.