Well, after reading this thread, and then the one about Oathkeepers and their "permit" for Lexington Green, a clear pattern can be seen.
Martial Law in Boston, for the "public's safety".
Denial of Free Speech at Lexington Green for the "public's safety".

Seems we're now trading Liberty for safety.
Of course, we'll get neither.

I could "sort of" see closing down public transportation, and emptying the streets, for both "public safety", and to deny the terrorist the ability to freely travel amongst the citizens, hidden among them.
But at this point, they know who they seek, and, more importantly, they know all those people dragged from their homes at gunpoint and then searched, were not the one being sought, and yet did it anyway.
It merely made for a good "sheeple training" opportunity.