...Unless he is going to lie to them.
For what it is worth, I generally encourage something like this as a maneuver, because it doesn't fall under declarations per say. Most importantly though, when a player asks me how he should do something like that, I try to think if it would be:
a) Something that we could imagine the character saying ("Hey, Chuckles, there's three of us, and we just took your boys out like they were week old garbage. Feel like talking yet?")
or
b) Something that is just a fact of reality, not directly tied into the actions of the characters, but that others might react to (In a war zone, it might be reasonable for a character to ask if it was noisy, and for me to then place the aspect CONSTANT EXPLOSIONS on the scene, or GODDAMN TERRIFYING for that matter)
This seems to fall in the a) category for me, which means I would want to treat it as a maneuver, because it is the result of an action by one character designed to influence another. This is the sort of thing I think one should be able to defend against, because there's a big difference between a corner drug dealer and John Marcone, and being outnumbered shouldn't affect them both the same.