Well, I think this often has to do with the bullshit idea that virginity, as far as women are concerned, is valuable and still has to be protected and uphold. Historically speaking, this has a loooong tradition that still not only has a huge impact on the present, but still IS present: Women are often shamed if they have multiple partners out of free will, many women are "proud" of their virginhood and there's still this underlying feeling of the men in the family wanting to protect the woman's virginity because they feel like they have actual agency about what a woman does with her body, which is stupid and bullshit, but even women are still taught to think and feel that way, thus they are proud of their fathers for "protecting" them and feel like they should "spare" themselves for the "right one". I don't want to bash anyone here, it's fine and great to be proud of something you feel appropriate to be proud of, I just criticize that the whole underlying concept is weird, to say the least.
So, in general I'd differentiate whether fathers / brothers are overprotective because they feel their daughter / sister need to be protected of the "bad men out there" (which she can totally do on her own) or because they are worried about the person itself, because they are shady, have a bad rap or something like that. This doesn't devalue romantic relationships because often this kind of obsessive overprotection doesn't reflect that the potential love interest is bad, but that the aggressive protection squad is blinded by their idea of righteousness and don't believe in the daughter's / sister's intelligence to know who is good for her and who isn't and her ability to make decisions for herself - which she always should, no matter whether the guy turns out to be good or bad, the person who wants to date him has to choose, no one else. If someone has good reasons to dislike someone because they've shown shitty behaviour and they express their unhappiness about the person by telling the woman who dates said guy, that's totally fine and healthy. If someone forbids a woman to choose a guy for herself because they feel uncomfortable about their sister / daughter being with someone on the stupid basis of "she's with a guy", that's THEIR problem and they should get over it because it's HER life and HER choices.