As an ASM, I've been working for a company that has a Resident SM who feels strong ownership of the space and is quick to call people (including directors) on moments that are unproductive to rehearsal. When things get tense, she will almost always call a ten and make everybody leave the rehearsal space, even if it's just to a lobby, dressing room, whatever. Then, while she deals with the person who has caused the issue, I check in with everybody, to make sure that they all have what they need and are going to be okay for the rest of rehearsal.
I think this tactic works very well - especially making them get out of the space with the negative energy, which also makes people step away from one another.
If it continues to be an issue, is there a Producer/Artistic Director you can talk to if you don't feel comfortable speaking one-on-one with the Director. A negative rehearsal room quickly becomes toxic, and it's best if everybody can feel safe and able to work.
(Also: I always keep 2-3 stress balls in my kit. If I see somebody starting to tweak, I toss one their direction.)