It can be reasonably argued that the intent of this malicious and demonstratively false utterance was inflamatory--and that, given the highly polarized and volatile situation, the utterances could incite others to displays of hostility that might escalate to personal violence.

Your comparison, Rabbi Sol, is flawed. If someone was close enough to the President to impact his physical well being, and they shouted out inflamatory acccusations of the type that you describe, their would be immediate action---
These false utterances could incite others to confront Ms. Greenbaum when she goes out in public, to vandalize her home, to make threatening, anonymous phone calls, and other such things--in fact, it may have already begun to happen.

Think about this---deliberately false statements are not protected under the law, utterances intended to inflame are not protected under the law--