It is a problem because it is an explicit sign to women thinking of applying to that company that they would not be welcome in the organization. Fewer organizations that welcome women mean a less attractive industry for women, which is the polar opposite of avoiding gender inequality.
Pretty much any time you're discussing inequality, if you reach for "it would be OK if the situations were reversed", you are choosing to ignore the substance of the problem, which is that 99.9% of the time the situations are not reversed.
Unwelcome? I've never understood this. The stereotype is that attractive people got hired by being attractive (or maybe for putting out) rather than being competent, but I have trouble believing anyone has never met any coworkers who were both. I've had my share of crushes on sharp people I've worked with; it's my responsibility not to let it be an issue, and so I don't.
It is a problem because it is an explicit sign to women thinking of applying to that company that they would not be welcome in the organization.
Is it really, though? If so, why? Men who enjoy going to Hooters are not necessarily crude, aggressive louts who treat women poorly. And a company that has lunch at Hooters is hardly a place where women are automatically unwelcome, or treated as inferior. In fact, I see very little connection her at all. As a man, I find that appreciating beautiful women and celebrating sexuality are completely orthogonal to my desire to treat women as respected peers and colleagues in the workplace and to treat women with respect based on factors other than their physical appearance.
Even the post I replied to admitted that it would be a problem if there was a woman in the company who objected. If you assume that women are more likely to object to going there than men, and that men in the company enjoy going there, it's obvious that a woman would be less welcome to join the company than a man. I think you're seeking to interpret "unwelcome" as implying deliberate slights or cold shoulders, which isn't what I was getting at - I mean that the company culture would have to change more to accommodate a woman than a man, and that this would be obvious to the woman.
Pretty much any time you're discussing inequality, if you reach for "it would be OK if the situations were reversed", you are choosing to ignore the substance of the problem, which is that 99.9% of the time the situations are not reversed.