What I mean by this is this person is seemingly nice but when you really look at what they said or listen to what they are saying there is small, almost hidden, insulting remarks. Often times manipulative people do this to, I assume, destroy the self esteem of their victim allowing them better control. So the sentence is mostly nice but there is one small thing about it that is really mean and fairly unnoticeable but when you hear it enough it can become rather daunting and make changes to your personality. Almost like slowly chipping away somebody like a stereotypical verbally abusive mother-in-law. Sorry for not having an example, I am really stuck on this one.

Edit: Did not see the autocorrect in the title, that is supposed to be someone, my bad.

Edit 2: I am noticing a lot of people commenting on what this type of person is being but that is not what I am looking for. So yes, the person is being passive aggressive, condescending, snide, et cetera but I am looking for a word to describe the situation. More psychology based, I should have clarified more

I'm trying to find an adjective to describe a character in my in-progress novella who's kinda rude and dismissive toward the protagonist, but they're aristocrats in early 19th-century Europe (protag is a princess), so he has to mask it with layers of insincere politeness. Think Jane Austen antagonists who make backhanded compliments and have to at least pretend to be polite when they're being rude.

(lmk if this post should go in a different subreddit, I'm new at this!)