Alt-right has become fascist not because of its ideology, which barely exists other than as a set of random (though mostly justified) reactions against the left.
It’s fascist because it’s adopting the left’s methods:
- the allegedly noble ends justify the means, however wicked;
- you can’t make an omelet without breaking a few eggs;
- violent crime and lying are appropriate tactics;
- yelling insults to people substitutes for argument; and so on.
Alt-right is yet another abortive anti-left movement. It has no chance of success, but it will do its share of damage before dying.