Timothy McVeigh had freedom of speech, I'm not sure how he plays into your example. He was lowkey because he was a radical, paranoid anti-government lunatic, not because he was "silenced". We have white supremacists freely running for office and one sitting in the oval office now and all I've seen is death and destruction even with their "free speech", even as they try and deny free speech to others.

Then of course we have Germany which has the strictest speech regulations specifically against Nazis and they have yet to collapse into dystopia; on the contrary, they've dealt with far fewer Timothy McVeighs, Dylann Roofs, and other white supremacist killers than we have. They certainly seem to have more stable leadership too.

Not saying free speech regulations are good or bad, but the notion that limiting free speech directly correlates to worse radicals and outcomes is pretty unsubstantiated.