2pairs vs nit aggression

I do not get it - what stops you from raising the flop? FD, SD, Pair hands possible...

As I said I dont expect him to lead from flop with TP even. So I'm giving him 2 pairs (KQ,K6,Q6) and sets (KK,QQ,66). I'm expecting from him to x/c his FD and SD.
Since he is so tight 18/14 from 20k hands I'm giving fim KQs and 66 only as a preflop calls. Why to aggres him when we will be behind, and even call

If you give him only 66 and KQs, why do you call the flop then?

Man, this is a mw pot he connected in some way and donks. You can raise him.

I like it as played. I'd rather bluffcatch here than inflating the pot. Nits don't lead with draws in my experience

If we put him on such a tight range, calling river is not ok.
I think raising flop would be ok.

I think KJ, KT might donk this flop, since he is multiway.

There's only one possible combo of 66 for villain so, even though it's in his range, I agree that you should raise flop, if he re-raises you have an easy fold.

Vs a nit I don't like raising the flop because I don't see him donking with a draw. I also feel that we have to fold at some point by the river, probably river but maybe even the turn vs such a sizing.

He can donk Kx and we beat all but KQ...

How many hand do we have vs this opponent? What is his Agression Frequencies by the streets?
By default I would fold the the turn, yeah, it is nitty, but your opponent double donks in multiway pot, if you don't have any reads vs this opponent, you probably should fold at least at the river.

Just to note: If you thought your opponent have only KQ,66 you definitely have to fold.