I don't equate compliments about the attractiveness of a lingerie model with domestic violence.
Neither do I, but it clearly has something to do with his attitude toward women, i.e. that they are less worthy of respect than men and that they exist to some extent for the sake of his pleasure of viewing them, similar to a sports car or a fancy new jumbotron.
I don't think that's true, at all. Saying a guy has a hot wife doesn't mean that the wife is somehow a possession or a lessor human being. That very likely is the case with Greg Hardy, but I don't find the comment to be particularly offensive. Heck, President Obama said worse things about Kamala Harris (i.e., "by far the most beautiful attorney general in the country"), but I'm not going to say that that says something about his attitude toward women, other than that he is attracted to members of the opposite sex.
I understand where you're coming from. Stating something ostensibly complementary about somebody else's appearance is on the surface a "nice" thing to do, not a negative.
Try to think about it in the context of society at large, though. The vast majority of what gets said about women in our culture is a commentary on appearance, with the underlying implication being that a woman's appearance is her most important attribute and the primary source of her value.
I think objectifying other people is pretty much impossible to avoid. We're wired for sexual attraction, and so we regularly see other people we find attractive without knowing anything about them as people. We think about their bodies and not the person.
I just think that going out of your way to mention it like that, when it's not even the topic of discussion at hand, is almost an aggressive move, like you're making a point to stake some kind of claim to objectify another human being, and enjoy doing it. Sort of implying that that is what she exists for, to be admired, much like an expensive sports car or a huge plasma TV suspended from the ceiling of a sports arena.
It's similar to when sports commentators take time in their broadcast to stop and comment on women sitting in the stands, like that has something to do with the game. Why do it? Why do you think it's a polite or respectful thing to say? I know it seems like making a big deal out of a seemingly innocuous comment, but it's an opportunity to challenge an underlying assumption that I think is at play, which is that women exist to be enjoyed as objects, first and foremost.
And of course, all of that looks a lot worse when it comes out of the mouth of an unapologetic domestic abuser like Greg Hardy.