I'm worried that figure isn't going to survive this encounter, I guess the same applies to Sensei, but he did dig himself into this one.
He told a lie to save himself from embarrassment, sure.
Did that lie force his students to act like a bunch of possessive psychopaths? Not really.
The situation getting out of hands is on them, I'd say, cause they're the ones who are so pissed off at the idea of Sensei having a date they'll pull out the firearms, despite knowing damn well he's far less durable than they are.