I agree fully that the Left abandoned its principles of tolerance when it embraced (and far worse, enforced) political correctness and Identity Politics. And the tactics they have used have contributed significantly to the mess we're in now.
I also know that the Right has been fully guilty of intolerance as well. And I truly don't care which side is "worse". When the shit is coming out of both ends like water through a fire hose, I'm not worried about deciding which side is "worse".
Until and unless both ends of this honestly look in the mirror and hold their own accountable, this continues, and so does the decay.
What we're witnessing -- not to be over-dramatic -- is the winding down of traditional Western civilization. It's not a plot by anyone. It's a profound, deep social change. There is a superficial view that all social change is progress, but that's a quasi-religious view, a secular version of the idea that there is a benevolent supernatural creature watching over us. (Given the terrible realities of human history, if we
are the objects of the interference of a some supernatural creature, it must be a very cruel sadist.)
We still use the terms 'Left' and 'Right', but they're really outmoded. The Left used to mean, roughly, those who wanted to change government in order to favor the bottom half of society, whom they saw as unfairly disadantaged: old-age pensions, trade union recognition, votes for women, fair treatment for racial minorities. Conservatives tended to resist this, and finally accept the changes after a period of time.
Now, with respect to things like old-age pensions, the legitimacy of trade unions, votes for women, fair treatment for racial minorities -- conservatives have generally accepted the liberal reforms. A few conservative politicians try to nibble around the edges of these things, but no serious Republican politician proposes, for example, the repeal of Social Security. A fair number of conservatives, at least those who post online, pretend to be libertarians in their economics, but they're just seduced by the attractions of a simple ideology.
Now things have inverted, literally, not just in political stances. The top half of society are not only the wealthy, the property owners, the independent professionals, and those who aspired to these positions -- it includes them, but is now mainly made up of the college-educated. They're the employees and much of the market for the biggest modern hitech corporations.
All of these people benefit from globalization, and mass immigration. They can support defunding the police, because they don't live in neighborhoods where violent crime is common. Their soft, cocooned life means that they don't appreciate the hard realities of international relations, where 'blood and iron' really are the final arbiter, so the idea of Marine rifle companies accommodating nubile young women, homosexuals, and transgenders is fine with them: let social justice be done. (The fact that those Marine rifle companies will probably never have to be used in defense of the US, due to our amazingly favorable geography, but only in our wars of choice abroad, supports this indifference to military efficiency.)
Ideologically, what we're seeing is the ultimate expression of what made the West different from the rest of the world: individualism, individual rights. We're being hoist on our own petard.
It's UK-centered, but there is a good recent book on what's happening to us, well worth reading: Matthew Goodwin's
Values, Voice and Virtue. He's a professor of politics at the University of Kent, and has studied the phenomenon of populism and its rise over the last couple of decades. He's on the Left side of politics, but has a deep appreciation for what is driving those on the bottom.
[https://
www.amazon.com/Values-Voice-Virtue-British-Politics/dp/0141999098/ ]