There's an article with a similar issue to this that just hit the front page, and it mentions the "paradox of tolerance" or "Popper's Paradox". Namely, if you are tolerant of intolerance, the intolerance will win out and the tolerance will disappear. If you give excessive freedom to propagate tyranny, tyranny will take over, thereby destroying all freedom. For this reason, force is sometimes necessary to stop force. Or, to use the colloquialism, fight fire with fire. Fight firepower with firepower.