There's a fair amount of channer types who are into femboys just because of the taboo, and the fact that anime femboys are often drawn indistinguishable from women. The idea that it's "wrong" is part of the appeal to them, and they hate it when people are proud/unashamed of themselves because it ruins it for them. Like they hate LGBT people, but for them, the defining trait of being gay isn't being attracted to the same gender, but not being ashamed of it.