I'd rather have someone spew filth out of their mouth in the public forum (the street, etc) than shoot me and my wife with a pistol.
How about having neither happen?
The reason why I say that hate speech is not destructive is that speech itself is strictly communicative. When one takes action, then the actions become punishable. but as long as one just speaks and DOES NOT ACT, then where's the harm?
There is _psychological_ harm.
And it not only hurts individuals, it directly affects the community's functioning. Hate speech, as you say, communicates hate. People who feel hated experience distress, which reduces their productivity. In particular, it makes cooperation much harder. And our goal is to COLLABORATIVELY write an encyclopedia. Hate speech is therefore directly counter-productive.
-- Fredrik