If you had been yelling that you would be happy that someone's house burned down, I suspect you would be a suspect in the event that said house burned down. Does that mean we are stifling free speech that hopes harm on people?
I can see some concern over this, but just not in this case. If it was, "all people that searched pyromancy" and that included people that were looking up fireworks, for example. Or if it was all people that looked at any house on redfin in that state.
This was a fairly targeted search, all told. "Anyone been asking around about the victim?"