Quite frequently, at least given the language they use around some of it, they demonize it because they fetishize it. Given the general anti-sex bent (usually for Christianity-based reasons) of the far right, it’s a “temptation” they have to resist, which then puts the fault on the “tempter”, not the person with the fetish they can’t accept is fine to have.

I was raised in a conservative family, and one of the things that made me a whole lot better was that it’s fine to be into weird shit in bed. Not saying that’ll always be the case, but it is part of it. Some of it is just people who’re grossed out by feet thinking that it’s a moral failing to be into feet, some of it is people who’re into feet and feel guilty about it. Guilt, and shame do things to a person