What should I have said next?

This morning I helped with, or at least shoved my nose into, a fairly ugly altercation that was happening at my local bagel place. I didn't hear the beginning of it, but basically this man was yelling at the women behind the counter (one of whom I've been buying bagels from for years, and who I like), calling them cunts and assholes and threatening to get them fired. He was not satisfied with the information they gave him about how to give feedback to the bagel chain, was not satisfied with the manager ("where's the REAL manager?") and was really being loud and acting vicious. I walked over and addressed the employees, asking if everything was okay or if they needed me to call the police. The man said "oh you want to get into this too, huh? What's YOUR name? [I told him] You must be one of these man-haters, right?" "You are threatening these women. It's not okay. I'll be happy to call 911", says I. "I'm not threatening them! Yeah you hate men. Probably a lesbian. Bitch." he says, prompting a male customer behind me to speak up with "Well I'm not a man-hater, and you're creating a nuisance" or something of that sort. I think he felt outnumbered, because he eventually left, making threats about getting people fired all the way out.

Here's what's still bothering me -- in my efforts to stay calm-but-forceful, I messed up; I shouldn't have said he was threatening anyone. I've racked my brains and I don't actually think his insults were threats; he did say he was going to get them fired by giving feedback to the "real" manager, but giving feedback is within his rights as a customer. I'm sure I did the right thing by walking over to the argument, especially since the employees thanked me afterward, but I didn't say the right thing to the guy, and what I did say could have been considered slander or something in court.

I wish I had said this: "I heard a disturbance and came over to make sure everyone was all right", which I more or less did say. But when the guy addressed me, what? I could have said "You have the information you need to give feedback to the company; is that all you need?" but then he would have done the lesbian/manhater rant, and it would have had to be followed by something else. What would you have said?

Thought experiment: new operating system

I recently asked the same question of several software engineers: Say you had to spend significant time working with a new OS, one you had never seen before. What would you have to learn before you felt pretty comfortable facing your workday?

( Why I asked; why I hesitated to ask )

And the interesting thing is, I got some flak about the question, but only from my younger colleagues. I quote one whippersnapper as saying, "I don't plan to ever have to do that again". My older, more experienced coworkers said things like "hmm... I usually X, Y and Z".

( the partially organized list of things people said )

I would welcome additions to the list from you geeks out there.