"Romantic?" Hermione said. "They're both boys!"

"Wow," Daphne said, sounding a little shocked. "You mean Muggles really do hate that? I thought that was just something the Death Eaters made up."
— Chapter 42: Courage

In other words, the wizarding world is sufficiently accepting of same-sex relationships that Death Eaters could use the idea that Muggles are homophobic as a somewhat believable slander against Muggles.