I try to be supportive of anybody, and generally go out of my way to be inclusive. I also make really stupid, juvenile jokes, although I am audience-aware.
In this case, his audience was the guy he was sitting next to, and there was nothing overtly threatening in the joke. In fact, if anything, it'd indicate he was gay and not at all interested in the woman in front of him who overheard him.
Ultimately, and this will likely get me in trouble, but I think she handled this in the absolute wrongest way possible.
(Reading the old https://amandablumwords.wordpress.com/2013/03/21/3/ response post largely sums up why I think it was wrong, but I wasn't aware of the other times she didn't bother trying to resolve things in a way that might actually produce positive results.)
The threats made toward her are obviously reprehensible; I don't understand that reaction either.