The left is not quite right that speech can be violence, but they are very close to being correct. The fact that we have libel laws shows we know this to be true, a person can be damaged reputationally & financially to the same extent as being beaten up, using words.
However, the left tends to treat violence in speech outside the question of fact. That is to say, the right accepts that even if a fact is true and violent it may be said, but it is wrong—as with Streicher or plain libel—to invent harmful “facts”.