The phrase "condescending tone" means that someone is speaking in a way that suggests they feel superior or they are talking down to someone else. Full definition
It made it all worthwhile, with the pacing of it and the almost condescending tone of the instructions making the overall shock value all the more effective. (useapotion.com)
Noxon and her team deserve credit for eschewing a frightening or condescending tone in favour of something more life - affirming and hopeful. (birthmoviesdeath.com)
My stomach was a bottomless pit and it helped coz I hate it when people say with condescending tone, «You're so skinny. (glamdevils.com)