A condescending tone or overly sarcastic response to a question being asked. I also don't care for people who feel the (need) to yell when frustrated or in order to get a point across. It has the potential to lead to serious consequences including ending the relationship.
Insulting or "talking down" to a mate is a form of verbal abuse. If one is not careful they'll lose them self. They become afraid to ask questions or they second guess their every action for fear of upsetting their mate. No one should put up with that crap.