Your premise is a little off. This is not exactly private property, but a public accommodation (https://en.wikipedia.org/wiki/Public_accommodations_in_the_U.... That is why MSG likely has to meet ADA accessibility construction standards, among other things. Different laws apply when you invite the general public into your property.
The law is like code. If you say, "persons I dislike" but you mean people of color, you have Jim Crow, which is deeply immoral. On they other hand, your point #3 is clearly valid. To resolve this, 42 U.S.C. ยง2000a talks about protected classes (https://www.justice.gov/crt/title-ii-civil-rights-act-public...). People with good and bad intentions have been arguing ever since then about what is a public accommodation and who belongs to protected classes. In this case, even if it's legal, MSG is not being terribly smart to 1) use dystopian technology to enforce bans 2) be petty and expansive about banning people 3) do so against a now-very-angry legal expert.
The law is like code. If you say, "persons I dislike" but you mean people of color, you have Jim Crow, which is deeply immoral. On they other hand, your point #3 is clearly valid. To resolve this, 42 U.S.C. ยง2000a talks about protected classes (https://www.justice.gov/crt/title-ii-civil-rights-act-public...). People with good and bad intentions have been arguing ever since then about what is a public accommodation and who belongs to protected classes. In this case, even if it's legal, MSG is not being terribly smart to 1) use dystopian technology to enforce bans 2) be petty and expansive about banning people 3) do so against a now-very-angry legal expert.