You can certainly interpret the killing that way, but there are many other reasonable interpretations, and to get a conviction you need proof beyond a reasonable doubt. Do we have a quote of him saying before the murder or publishing at any time something indicating that he was killing this guy to send a message to all the evil m************ who act just like him? If we do, your conclusion is warranted. If we don't, your conclusion is speculation.

Let me give you a parallel. Imagine someone cuts me off in traffic and I pull out a gun and I shoot them. Am I terrorizing other bad drivers? Probably not. Probably I'm a psychopath dealing with road rage in a terrible fashion. In other words, the fact that other people can draw conclusions about similar behavior does not in itself make my actions threatening to them in any way.