The answer to “at what point” is when it becomes inciting or likely to incite “imminent” lawless action. Imminent means that the very nature of the message prompts someone to do something right then - it is that compelling in its message. Somebody saying “immigrants eat cats” may at some point cause violence but it certainly isn’t tailored in its content to cause or intend to cause someone who reads the message and feel compelled to violence right then - even though it may be part of someone’s mindset that eventually turns violent.
The problem is that It’s easy to say that a new standard is needed but the devil is in the details. Who decides what is false and intended to cause violence and in a way that will not be commandeered by authoritarian forces? I think that’s the biggest risk: an obvious unintended consequence of criminalizing speech is that the more speech is criminalized, the margins become more easily manipulated.
For example, if a social media message saying we should go to Washington to protest a president’s immigration policy goes viral and creates a real protest that becomes violent, could the government then decide that future such messages are inciting violence and prosecute the next people who post similar messages?
The Bill of Rights is grounded in protecting individuals from government abuse - so that always has to be the starting point. Would changing the standard make it easier for the government to criminalize speech it doesn’t like? And we have seen that we cannot presume the government will act in a just way.