My (F23) friends keep saying my boyfriend (M24) is ugly.. but he isn't?

Since the beginning of my relationship, my two close friends have said to my face and also behind my back to each other that my boyfriend is "ugly" or "not even cute". But the thing is my boyfriend is conventionally attractive, his guy friends think he's good-looking, strangers occasionally complement him, and other girls have said so as well. I obviously find him attractive, and I know that what truly matters is that I love him and enjoy being with him. Looks have never mattered to me in relationships, and that still hasn't changed.

Still, I can't help but be bothered by my friends' comments. It makes me feel bad, and I'm trying to understand why my friends would say these things. I get beauty is subjective, but their comments aren't just neutral opinions but actively and constantly negative.

Has anyone else experienced friends trashing someone you’re dating, even though you know that person is genuinely attractive? How do you deal with it without letting it affect how you feel about your relationship?