don't be ugly 

Don't be rude, insulting, or make yourself less attractive by saying or doing something rude/insulting to another person.

Some people are beautiful...until they open their mouth and speak 'ugly' of others.

My Southern Mother would say this often to us if we were speaking unfavorably of another person. 'Don't be ugly'. Her meaning was, 'It only makes you look ugly/less attractive.'

don't be ugly by Rheej March 3, 2014