Which got me thinking:

As a bachelor I know if I went home to meet a girl's parents and her father treated me with anything too far to either side of of cautiously optimistic politeness (a sort of "I hope my daughter's found a good guy, but I'm not sure yet, so I should get to know him so I can steer her away or towards as required" attitude) I'd see it as a red flag.

If he responded with the sort of fawning automatic approval you sometimes see in Hollywood, I'd worry that he'd been spoiling and fawning on "his little princess" her whole life and as a result she was likely an emotional cripple. (And he would likely cause any marital strife to escalate by encouraging her to take any of my failings, real or imagined, out of proportion)

On the other hand if he responded with the sort of cartoonish authoritarianism that these guys at least joke about, then I'd be worried that if the man who knows her better than any other automatically assumes that she's going to have freaky sex with any random arsehole who turns on the charm, perhaps I should take him at his word.