No worries Salmon; I don't actually propose Killbots as a solution to any problem... at least that I can think of. However, your statement got me thinking:
If your reasoning isn't strong enough to nullify opposition on its own merits, then it isn't strong enough to justify eliminating opposition by force.
Do what you believe is right. Encourage others to do the same. Sharpen your critical thinking and communication skills. Be just as critical of yourself as others. This is the only path to change that doesn't undermine its own good intentions.
You've outlined several beliefs I share in how to live a life well. Still, there are times when you are opposed by someone who is not arguing from a platform you can even approach, much less refute. Sometimes, people believe they have the absolute truth, without any test in reality... circular logic that, to them, proves itself. This brand of thinking has and continues to lead people to belief in the innate inferiority of people of different races, religions, or cultural practices. Arrogance, dogma, and ignorance have lead countless nations to war and genocide in the past, and as such there was no basis on which to "nullify the opposition on its own merits", because the belief is ultimately baseless.
There are times when force was the most expedient solution to eliminating that opposition. It's perhaps not the only solution, nor an ideal solution, but military action likely prevented decades of loss and death in World War II, as opposed to what a lengthy diplomatic appeal to the hearts and minds of the German populace (and the ensuing propaganda battle) would have.