You can't defeat the Alt-Right without understanding why it came about.
When a Republican is wrong, it's usually because he's ignorant of some scientific or cultural concept. When a Democrat is wrong, it's typically because he's too elitist and dishonest to even CONSIDER an opposing point of view. Until the Alt-Right came along, Republicans tended to be humble, respectful, honorable people, whereas the Democrats would break every rule of decency, decorum, and principle just to suppress the other side and win.
The Alt-Right gained traction because a subset of Republicans were tired of watching their party behave respectfully and honorably, and then get treated like shit and lose over and over again. That's why they call their fellow Republicans "cucks." Mitt Romney's loss was the final straw in this. They realized that in order to win any victories against the Democrats, they have to sink to their level. They have to be boisterous, aggressive, insulting, hypocritical, unprincipled and bigoted. Yes, that's right: The Alt-Right is nothing more than a movement of Republicans who decided to deliberately start acting like Democrats.
The sad thing is, it worked. It helped the progressives win countless victories for decades, and now that same approach is winning victories for the Alt-Right. Now that Republicans have had a taste of victory, they're going to keep doing this until the Democrats are completely beaten into humble submission. The Alt-Right will only stop when the Democrats are willing to admit that they've been the worst kind of assholes for over a century. The U.S. government was founded with limited, enumerated powers for a reason- to avoid sadistic group warfare via politics. If the Democrats are finally willing to learn that lesson, the Republicans would be happy to return to that type of system. But until the Democrats DO learn that lesson, the Republicans are now going to use the power of government to wage total war on the Democrats' voter base. It's up to the Democrats now to learn their lesson and end this war, or continue suffering crippling defeats.
So Democrats, what's it going to be? Are you going to keep behaving like dishonest, elitist, entitled little shits, thereby feeding the Alt-Right? OR are you going to learn a more mature approach to dealing with political disagreement and learn to compromise and show respect for other people, draining the Alt-Right of their power?