The alt-right is basically a reaction to what's viewed as the ineffectiveness and "cuckoldry" of the mainstream neoconservatism that dominates the Republican Party et al. Portions of what we call the alt-right have also generated a rather comfy synthesis with white nationalism. I think the roots of the alt-right are online. I can see roots in the neoreaction movement (aka "Dark Enlightenment") as well as white nationalism and its influence on right-wing chan/meme culture. The loudest online proponents of the alt-right that I know of are avid participants in online meme culture, so it's rather hard for me not to see the whole thing as growing out of it. These people just needed an identity to latch onto and the Trumptrain to grab ahold of, and that's what they did.
That's just what they tell the normies, fam. It isn't a reaction to neocons (who the hell cares about neocons in 2015/16?), but the American white nationalism of /pol/ having developed a political voice and converged with some older Nouvelle Droite types like Richard Spencer and Greg Johnson.
If there's any reaction that has propelled the alt-right, it's SJWs.
The alt-right has no relation to NRx, although in practice it has assimilated a good deal of it (like Butch Leghorn and the ethnonationalist camp in general). NRx is a distinct subculture of its own with people like Nick Land and the authors of Social Matter and West Coast RXers criticizing alt-righters.
The alt-right has a distinct culture that goes along with it that I think /really/ defines it more than its views because the alt-right is a movement of people who hold interrelated ideologies reacting against establishment conservatism as well as leftism. Many people have had these exact same viewpoints before the alt-right existed, and continue to hold them without being part of the alt-right. Ideologically they tend to have restrictionist immigration views, anti-trade views, and a hatred for what they see as political correctness (their anti-PC stance basically being their only merit in my view). And let's not forget they almost invariably support Donald Trump for president, another defining hallmark. When one digs further it's not hard to find explicit racism but this doesn't necessarily hold for all of the alt-right, and the racists actually rather dislike that their precious movement might be "co-opted" by people who are merely xenophobic.
The Donald Trump bandwagon was more of an opportune strategy for popularization; it got misinterpreted as being some defining characteristic. Actually a great many alt-righters are pessimistic or indifferent over a Trump presidency for demographic reasons or other.
"Explicit racism" is absolutely essential to the alt-right proper. As I said, you're operating under the exoteric creed ("alt-right is a broad tent against establishment conservatism") which is simply innocuous bait to lure in unsuspecting normies, although it was sort of true until recently. But again, by now it has unambiguously metastasized into American white nationalism+HBD. Just go look at Lawrence Murray, TRS and /r/altright. Hell, even the intellectual Counter-Currents has lost some of its interest in the more esoteric Conservative Revolutionary stuff in favor of straight WN, for strategic reasons.
I think these facts speak volumes about why the alt-right is so hard to define. You have everything from the blatantly racist pseudo-intellectual folks at American Renaissance to the dangerous faggot Milo and his buddies at Breitbart claiming to be organs of the alt-right. It's a diverse field united by their opposition to the mainstream in conservatism and left liberalism.
Milo isn't alt-right, fag.
>"blatantly racist pseudo-intellectual"
The only problem with Amren is their refusal to name the Jew, for which Jared Taylor will be ovened when the Day of the Rope comes.
(More seriously, Amren is plenty flawed but still more robust than you give it credit for.)
As far as their opinions are concerned, I tend to find myself at odds with them. These people tend to throw out the good parts of the libertarian-conservative fusionism that has pushed the intellectual development of the American conservative movement forward since Goldwater, throwing out the free market economics that libertarian economists have basically let conservatives borrow for over half a century. They're at best regressive on race, and at worst racists. The alt-right may be smart to bring a critical lens to our broken immigration policy, but their obvious anti-immigrant and anti-Islam xenophobia is unwarranted. Let's also not forget their loving support and fawning over real-life meme Donald Trump becoming president. I'll be the first to admit he was amusing to me too for quite a long time, but I guess most of the amusement has worn off (although I never really tire of seeing liberal tears).
Laissez-faire is anathema to a proper right wing.
I'm really confused as to what the left-wing Adolf Hitler has to do with rightism though...
We're all left-wingers after 1789.
(Also, left-right have never had any economic policy consensus.)
"Humanity Is Overrated" - Shrek