Nobody has said they can't go. In reality, people can choose to not wear a mask if they so wish, it's the right, but my personal opinion is why wouldn't they?
It's at most a small inconvenience to wear when travelling through the turnstiles, the concourse or toilets to help reduce transmission or simply to reassure.
Just because you can do something (not wear a mask) doesn't mean you should because morally I see it as a way of supporting the entire population.
The club could however make it a condition of entry as per their own T&Cs or code of conduct.