I'm pragmaticly leftish, so I can certainly relate to this well-intentioned message.

Unfortunately, the facts don't agree with lofty idealism.

Whereas classical artists sought to depict humanity as close to perfection as possible,

Virtually every human if the planet would increase the level if attractiveness of their mate; if they could. Anyone stating otherwise is being polite.

the modern world finds disease, illness, and disabilities to be far more alluring.

Every human on the planet would eliminate/ameliorate the disease, illness, and disabilities that affects their mate.
I would question the motives of anyone who did not feel this way.

Keep your sister away from the guy who is allured by the diseased and disabled...