Politics

This is my stance on it too. People like to treat today's political environment as two sides of a coin diametrically opposed, but that's not how political ideology works, it's more nuance than that, like a sphere. I get why American's do it with a two-party system, but that doesn't mean you're all in on one or another, people are more nuance than that too. People who run with this mentality that there are only two sides to politics often fall into the mistake of equating to two as equal sides as you said. It makes it hard to acknowledge the difference of the extremes and their intentions.

Though I think the biggest reason people are less tolerant the alt right is because there are more reasons outside of politics to be against the alt right. Outside of politics, alt lefties usually get into arguments with economist and capitalist because extreme leftist have intensions to change the economic landscape. Whether for better or worse is precisely what they're arguing about. There's also the more fringe alt left (tankies I believe) who will get in a tussle with historians and survivors alike, but their conversations chill out once they realize no one's condoning anything (usually, idk all you tankies).

Meanwhile the alt right targets specific freedoms enshrined by the US constitution and the Human Bill of Rights. The alt right wants a say in who you marry, whether or not you should adopt, religious rule you should abide by, who should/shouldn't get to vote, whether the vote should be decided by the people or legislator (you now Democracy and all), your identity, your medical decisions, your family planning, your education, and the very books you read. There's a desire to snub out individuality if it doesn't abide by the alt rights idea of "normal." All of these stances directly invade individual rights of many people and their ability to pursue their respective happiness. While there's political reasons to speak out against these stances, there's also moral obligation and the simple instinct of survival pushing back on these perspectives. This creates a large group of people who not only disagree, but whose existence is literally threaten, there's no room for tolerance when lives and freedom are on the line. The reason alt right has a tough time is because most Americans still hold age-old American values of liberty, life, and the pursuit of happiness.