Easy - people are generally very possessive of their opinions and often times have difficulty accepting that others have differing tastes. You think your opinion is "right" yes? Otherwise, why would you claim it if you didn't believe it to be the most reasonable?
Aside from that basic concept, there are a whole host of other personal and social factors that play into this shaming characteristic among male peers. Insecurity is a big one, as well as personal philosophies. Insecurity in that you are very protective of your taste in women and need to feel validated about it so you look down upon others to make yourself feel better. Personal philosophy for example - maybe you're a Darwinist and think it is unnatural and completely illogical to be attracted to women who are not thin and fit, or maybe you're racist and think it's wrong to be attracted to other ethnicities. The list goes on. I can't speak for weather or not this is more of a culturally dependent thing because I have not really talked-shop with men of other cultures.
Aside from that basic concept, there are a whole host of other personal and social factors that play into this shaming characteristic among male peers. Insecurity is a big one, as well as personal philosophies. Insecurity in that you are very protective of your taste in women and need to feel validated about it so you look down upon others to make yourself feel better. Personal philosophy for example - maybe you're a Darwinist and think it is unnatural and completely illogical to be attracted to women who are not thin and fit, or maybe you're racist and think it's wrong to be attracted to other ethnicities. The list goes on. I can't speak for weather or not this is more of a culturally dependent thing because I have not really talked-shop with men of other cultures.