The girls may not have been present for the conversation in Chapter 1, but Kitty and Lydia are told in Chapter 7: "From all that I can collect by your manner of talking, you must be two of the silliest girls in the country. I have suspected it some time, but I am now convinced."

So the girls' presence didn't cause Mr. Bennet to be any more tactful, even if he wasn't actually comparing them in Chapter 7. I doubt that their presence would have any difference in Chapter 1 -- that particular situation may not have been dire, but there were other dire situations, and Mr. Bennet shows absolutely no concern for his daughters' feelings -- at least, not these two.