Yes. Theoretically the most they can do is charge you with trespassing if you refuse to leave.
The key (in MA) is bolded above!
They have to ASK/TELL you to leave FIRST before anyone can be charged (in MA). You can be told to leave any public place for any reason and if you refuse you can be arrested and charged with criminal trespass . . . it has nothing to do with guns.
So if you conceal properly, nobody knows and nobody is going to ask you to leave, ergo no problem.