He must mean that it accepts cash and Bitcoin only, or he's full of shit. No way is there a bar that only accepts Bitcoin thats surviving, especially one the community doesn't even know about.
Apart from the fact that he'd likely go broke accepting Bitcoin only, I wonder whether it would even be legal for him to refuse to accept cash.
Legal tender laws only apply to settling debts. So if he refuses to server the beer until he is paid, does not allow tabs or serving before paying, then yes he can refuse customers that do not offer him the type of payment he wants. Now on the other hand if he had served some beer and then asked to be paid his customer is only obliged to pay the debt in legal tender.