I follow a local selling group. An ad has just popped up for a person selling an American bulldog pup, 22 weeks. Would I be sticking my beak in to comment and suggest a rescue rather than Facebook? I can only imagine this dog being bought to use for fighting.
IMO there'd be nothing wrong and a lot right about pointing out the non-wisdom of advertising any puppy for sale over the internet. But you'll probably need to be prepared for a flaming, to be told that you don't know what you're talking about, of course they'll only sell to a 'responsible' buyer, etc., etc.. I guess that there'll be an outraged response to your comment. If you're prepared for that and also see some value in airing your very valid opinion, then, yes, go for it!