There is actually a test for incitement set out in https://en.wikipedia.org/wiki/Brandenburg_v._Ohio - the standard is whether speech is likely to produce imminent lawless action.

Here, the question is whether a rational person in Trump’s position could have known that directing people to the capital and telling them illegal activity was going on inside are likely to promote specific lawless action at that destination, regardless of the specific words used or whether the type of violence is specified.

https://www.themarshallproject.org/2021/01/08/a-civilian-s-g... has a larger primer.