Why are people so judgmental of my relationship?

My (23y) girlfriend (18y) of 4 months now is really small. She has proportionate dwarfism, so from a distance she could be mistaken for a child, though up close she's clearly a woman. Due to her being super short but not being disproportionate the way most people with dwarfism are. Im fairly muscular and i'm 1' 5" taller, so I look huge next to her.

I've been facing a bunch of accusations of being a pedophile of some sort. Even though she is an adult, just because she's so little. I really don't know what to do. I love her, and wouldn't leave her. But I'm almost ashamed of public displays of affection because people give us some really bothered looks. I don't resent her for it. It's not her fault. But I find myself sometimes wishing she was a foot taller just so I could avoid the judgment.
Why are people so judgmental of my relationship?
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