In chapter 1 we have this description of Mr Bennet from the narrator: Mr. Bennet was so odd a mixture of quick parts, sarcastic humour, reserve, and caprice...
I don't think we can rely on any single thing Mr Bennet says to be a true reflection of his feelings - except possibly at times of duress, which we haven't seen him in so far in the group read anyway.
There are I think two things behind it:
- Mr Bennet could be cynical about everyone, male and female, regardless of age
- He's a generation older than his daughters, and he comes across as reasonably intelligent, so his daughters probably do seem somewhat silly and ignorant to him. I've noticed as I've started to have responsibility for training new graduates at work, how young they seem, and of course they have to be taught a great deal of things.
Of course, that the Bennet daughters don't yet have the life experience of someone 24 years older is unlikely to make any difference to Mr Bingley's evaluation of them, Bingley's also young.