People are dumb and visually driven. When they see someone who sets off their under-developed brains, they get angry and stupid. To most people, a monolidded Asian is read as the most disgustingly "Asian" to them, so they react in very "cave man" sort of ways - by singling out that Asian for harrassment, bullying, or violence. It's an immediate and kneejerk reaction.

Koreans and Northern Chinese are often read as the most "Asian" because they tend to have the most stereotypically Asian features, as in monolids, pale skin, and wider/bigger/rounder faces, as opposed to narrower faces.

Godfrey Gao wouldn't get as much (or any) harrassment, not just because he was very handsome, but also because his features were semi-Western - he had a long, defined face with a tallish nose and good, strong jawline.

Filipinos, Thai, Viet, and other Southeast Asians are more likely to get the harassment and violence if their facial features look more East Asian. A large-eyed Filipino with more Western looks is unlikely to get any harrassment.