It wasn't, though. He didn't respond to someone saying 'Well, SJWs, so there'.
He brought it up in a context in which it was rather appropriate. His presumable opinion on social justice advocates not withstanding, the whole 'it's sexism because he didn't let her interrupt him'
is, in fact, bullshit. And from what I could tell, giving him the benefit of the doubt here, he used it precisely as they're meant to be used; people who try to provoke outrage and indignant fury at things which deserve neither in order to get what they want within the progressive movement. That easily falls under the category of SJW, if we're using the negative connotations of the word.
Godwin's Law is also intimately associated with Nazis because of it's original purpose, which allows insinuation, and I don't know if you meant to, most likely not, that your opponent is equating [thing] with Hitler, which obviously makes him a terrible person and therefore his viewpoint is bad.
So, A, he didn't call anyone an SJW as far as I could tell, B, he was not shutting down a conversation with anyone, and C, he used it in an actually appropriate context if you argue in good faith.
If you define your opponent's terms, then call them out for using those terms in a context where your definition makes them look bad? I think it's obvious why that's poor practice.
Okay, so you feel that way. How would you feel if I said "I find that the Sanders camp immediately resorts to accusation of oppression/racism/sexism without any real evidence of such. Which is where I find they are very similar to SJW"?
I would believe you were wrong? Because as far as I'm aware, they
haven't done that, or even really pulled those cards?
I mean, they might have and I could be wrong, but just saying 'what if I said that to you' doesn't really get anywhere if it doesn't hold true for your opposition. Like, either they disagree, or they agree. And I'm not sure what point you're trying to make here. The whole 'you feel that way' bit seems somewhat patronizing, as well.