Private entrepreneurs should be able to do whatever they want. I don't go to bars but I might visit one with a 30+ limit.

I guess I'd have to disagree here. I think that there definitely should be some restrictions on who you can ban from patronizing your business (such as forbidding businesses from banning racial minorities or homosexuals); I'm just not sure whether I think something like limiting based on age (outside of enforcing the legal drinking age).

I'll try another thought experiment which is a bit more similar to the real-life situation: do you think that private entrepreneurs should be able to ban people over a certain age, e.g. everyone above 50?

There are bars like this in my city, in some particularly rowdy college-bar areas. They've been open for 20+ years, most of them. So it must work out from a business POV. But never visted one to report.

However, guess it's only news because it's New York. =)

These existed in Hoboken at one point. Haven't been there in years so not sure if this still happens.

Bars tend to already ban everyone in a certain demographic: Under 21.

Yes, but there's a a clear legal basis for that. I'm not sure there's a legal basis for banning arbitrary demographics from patronizing a business.