I feel like there's a word that I know but can't locate in my brain for regarding someone from a position of authority.
The word, in itself, is neutral (not negative or positive) so it's not really synonymous to condescending, but it's in that family.
Specifically, it would be the way a teacher would approach a pupil. Provided that that is the relationship, there's nothing negative about the interaction.
However, if one were to take the same tack in a situation where the party being addressed is not assuming a lesser expertise or authority than the speaker, then the speaker comes off as... [ this word ].