We already have done this over the last several centuries by defining the line between legal and non-legal speech. The point is the line is chosen to trade off these risks. There is no silver bullet but acting like there is, and that this debate is just beginning now, is fallacious.
Can anyone seriously argue that disinformation on Facebook isn't dangerous? The only possible question should be what can we do about it to preserve debate, free speech, etc. while stoping the literally deadly parts.