there is a thing called laughing with some one and laughing at some one. Seth was laughing with Weinstein and if you look at the implication of the joke. all five nominees had to put up with disgusting behavior and maybe a rape. . and those he was laughing at.
the other implication of the joke is that the seriousness of the situation was wide enough with those in the audience that a majority got it.
I think your assessment of this is very shrewd.