They cannot tolerate any deviation from the direction that they think the nation should be moving toward, even if that direction is completely foreign to the America envisioned by the Founders, the America familiar to and loved by most of the citizenry, and the America that ensures the rights of individuals to live free and self-determine.
Many of them hate that America and thought that it was on the way out. They don't see elections as a way of ‘tweaking’ government policy by degrees, to keep the nation strong and help everyone who calls the USA home. They want a revolution that transforms this nation into something they want it to be - even if it hurts 100s of millions.
There is zero question who the radicals are in this conflict, and it's not those who go to July 4th and Memorial Day parades. It's not those who think the flag is much more than a piece of cloth. It's not those who think that there are legitimate limits to what children should be exposed to in school, online, and by the ‘entertainment’ industry. It's not those who see America as the land of the free and the home of the brave. It's not those who see the Constitution as a bedrock of our existence as a nation and think it should be preserved - not circumvented.
It's those who don't want America to be America. They thought they had America on an irreversible course to be dismantled and rebuilt as what they want it to be - weakened and more recognizable to Marx than to Jefferson. They are blind to their own hate, but it is definitively hate that underlies their drive to transform America into something most of us don't recognize and don't want to call home.
Scratch the surface and you invariably find one or both parents of these people were tyrannical, spiteful, arbitrary, ignorant.
In other words, the 'apple' doesn't fall far from the horse.