Martlin Luther King Jr also had some ideas on how to make a difference. The authorities were mixed in their reaction, as were the people. In the long run, MLK seems to me to have had tremendous influence.

Ronald Reagan had some ideas on how to make a difference. The authorities as far as I know never had a major problem with him, and the people eventually came around. He had a LOT of influence (for example, national telephone companies deregulated around the globe following US's example pushed hard by Reagan).

My point is assassination is HARDLY the only way to have influence other than voting. And to the extent your post suggests there is some correlation between making a difference and being sneakily evil, it is misleading.