I fully agree with the statement; "Their wifi, their rules."
However,, if you are their "customer" in any form,, then you have the right to express your opinion, and if possible,, not go into their "business" again. A formal complaint letter to the hospital administrator, copied to the board of directors, and as many related places you can the have an "interest" in things may help stop this stupidity.
For too many years,, between the media, movies, liberals, etc demonizing guns & their owners, (unless they are the good guys,) we have become the "enemy" to them. If enough of us POLITELY express our thoughts & feelings in an intelligent manner,,, quite often things can change.
Example; A single business owner,,, who posts his public entrance against CCW. When polite & educated gun owners point out to them,, the legalities they may face if they do not provide adequate security for you & all their patrons,,, often they remove the signs. When shown that a CCW holder is a law abiding citizen, who has gone through a lengthy process to be allowed to carry CCW,,, is a better type of customer than the thugs who ignore the law & are often the criminal element they do not need in their business.
When presented with facts,,, in a very educated & POLITE manner,,, often they may re-think their policy of no CCW.
Now,, multiply it by many, many people entering a much bigger business,,, who politely complain, AND point out the many lawsuits they could face if they fail to allow you your legal right to self defense,, it can possibly make many re-think their position.
We have to fight,, in an educated manner,,, with facts & not emotions. That is the only way we can make a real difference.
I myself, often compliment business managers or owners when I do not see a "No CCW" sign on their doors. And if I happen to NEED something a business offers,,, and it's the only available place,,, I seek out the management, and politely, directly complain. I also express how I will be sure to let as many people know about their policy as I can.
In business,,, word of mouth,, combined with social media can & does have an impact.