What do you mean «Neither case would be good»? Not clear.

Example: Gary Marcus wrote six weeks ago, «single-minded obsession with cutting costs is going to cripple science and American universities, with horrific lasting consequences» - that falls into your «...actions being horrible for research», but how does it fit with your statement of a "good case".

I imagine something like neither case (of getting arrested for such) would be good

Speaking of statements open to misinterpretation... sorry, as the other commenter imagined, I meant that refusing entry for either type of statement would not be good, but one would be worse than the other.

Refusing a foreigner entry for inciting violence (even against people who are not Americans and not in the U.S.) would be perfectly fine with me, though I don't approve of demanding foreigners make all their communications available to CBP (which is basically how we got here).

I do wish we’d have better sources since there could be a range of jokes about the two shooters during the campaign which could get close to a plausible threat, but the fact that they just shipped him home makes that seem less likely. If you thought he was Carlos the Jackal you’d probably at least hold him long enough to investigate his travel plans and contacts more.