It might allow a return to that, but I very much doubt if the culture or the market would permit it.
That can work both ways. Sure posting a sign that says you don't cater to homosexuals - or blacks or Muslims or fill-in-the-blank - might cause some people not to patronize your place of business. But it might also attract customers with similar beliefs who didn't patronize you before. And it won't impact people who don't care one way or the other. And freedom of association is guaranteed.
None of that addresses the potential for harassment or violence that might occur as a result of such signs.
I have studied homosexuality since the 1990s, and while many homosexuals are able to function in our society without serious repercussions, there are a lot of them that are down right dangerous sociopaths. They don't have normal boundaries on the limits of their behavior, and they will act out, violently if necessary.
When they are "triggered" they often respond with acts far in excess of what a reasonable person would accept. I can recall any number of examples where they went hyper violent over very little in the way of provocation.
If you will study examples of when homosexuals are involved in murder, they are not simply content to kill someone. They must kill them with excessive brutality and violence. They won't stab someone once or twice, they will stab them 50 times. They won't bludgeon someone two or three times, they will beat their head into a paste.
Psychiatry rightly considered these people mentally ill, because their mental illness displays itself in ways beyond just engaging in sexual activities with other same gender people. (such as a propensity for suicide.)
You don't think establishments wouldn't put up "We do not cater to Muslims" signs? Some have already tried. Why shouldn't they be allowed to? Same with people who don't want to cater to other groups?
None of that addresses the potential for harassment or violence that might occur as a result of such signs.
OK so now establishments decides they don't want to cater to a particular group, they get taken to court, they get fined under current anti-discrimination laws. Where is that better than potential aggravation, which would be temporary and die out as this became the new norm? Long term it's the better solution.