Might not be a thing in the UK, Matt, but in the US the unspoken assumption is always: "If we white people become a minority, the non-whites will be able to treat us just like we treat them." Which, of course, would be AWFUL! 😱 Think separate rest rooms, water fountains, bus seatings, yada yada — just Google photos of "Jim Crow" in the 1950s.
As a non-parent of 66 years of age, married to another non-parent (but AWESOME aunt), I've also been grinding my teeth about all the attacks on people who (for whatever reason — I'd have been a total shit father, in my case) are not parents. I'm still waiting for anyone to offer real solutions, like ways to make it less freakin' expensive to have kids. "Wait, why should *I* have to pay for somebody else to have kids?" <sigh>