To demand ID requires reasonable suspicion of a specific crime. Just ‘suspicious’ isn’t enough.
These guys may be up to no good. They may be just exercising their rights - but until law enforcement can site the statute where a law is being broken they have no authority. Otherwise they’re just fishing for crimes and violating the 4A.
The gun laws from the 60s came about because of the fear of black people arming themselves during the urban unrest.
If these guys are just exercising their rights, then let them.
Reviewing MA’s gun laws, that seems to be the case. An alternate approach might have been for police to swarm the area and just sit...and watch. And keep watching. And photograph.
Does this work for you?
https://www.foxnews.com/us/police-identify-militiamen-armed-standoff