As I do it all the time, here is the answer by my 'not really intelligent' co-worker today when I was trying to explain that 'mademoiselle' in modern language suggests the woman is not married:

Ну-ну, теоретик ..ля. - Which somehow made it clear some 'patronizing' on my part was involved.

I like the notorious "Не учите меня жить" so wonderfully chosen by Файнзильберг и Катаев. Well most Russians know the phrase and where it comes from, but as I have used the real names of the authors I have been intentionally patronizing some Russians here, haven't I?

At the same time I would myself choose to say Не надо строить из себя умного. - cf. Don't be clever! (real life answer to me which I once heard).

If you don't know what 'cf.' stands for I am not going to explain that to you not to sound too patronizing.

PS. To Valda - only 1 meaning of the word is implied here (according to your question).