My point is that this is the same argument you’re leveling about ‘origins’ with the Taliban.

Lol, no it isn't bud. I'm not saying the US 'created' the Taliban, just that their support of islamic fundamentalism lead to the proliferation of islamic fundamentalist groups. If 'supporting socialism' involved arming and funding fascist militants, then sure - that involvement could be said to have lead to the growth of fascism. Similarly, if 'opposing socialism' involved funding and arming fascist militants (or islamic fundamentalists....), then that involvement could be said to have lead to the growth of fascism (or islamic fundamentalism.....). But 'socialism leads to fascism' would be an exceedingly dumb thing to say.

The Mujahidin still retained large stocks of US weapons, even if the flow had stopped.

Right.... And once the soviets had left, all the weapons and funding the US had dumped into the country helped fuel factional conflicts between competing fundamentalist groups.

The mujahidin were a diverse group united against the Soviet invasion.

I mean, maybe at the time? Once the war ended they certainly weren't united anymore. The only other thing they had in common other than their religion (and the only thing that mattered to the US) was their opposition to the Soviets. The US preferred this group over the secular militias because, in their view, they were less likely to install another communist or socialist government after the soviets were defeated.

Again, what is your position here? “The US supporting people against being massacred is Bad and the Afghan people deserve Blowback™ for accepting aid”?

Not at all. My position is that the US knowingly armed and funded religious fundamentalists in order to undermine Soviet influence, and that funding ended up fueling religious extremist movements that threw the entire region into chaos for decades after. Does that mean I support the Soviet invasion? Fuck no. But I sure as fuck don't deny the US's role in the formation of the Taliban and other militant groups that terrorized the country once the soviets were gone.

Child abuse is a sadly long-standing tradition in Afghanistan society, not something that Mujahidin ‘extremists’ just ‘starting doing’ after the Soviet-Afghan War.

Ok, so they were religious extremists before the US was supplying them with weapons, too? That doesn't exculpate the US from empowering them just because they were dead-set on stopping the spread of communism at any cost, and acknowledging that cost doesn't somehow legitimize communism, either.

If Pakistan had decided that reviving the Communist throwbacks was in their national interests, would you be decrying the US for creating Communist ‘blowback’ in Afghanistan and declare that the Mujahidin were the origin of the Communist terrorists?

If that made any sense at all, sure? The US was aligned with Pakistan during the war, and much of the aid was distributed to the groups Pakistan thought favored them. From the US's perspective, it didn't matter who was fighting against the Soviets, only that they fought the Soviets. If Pakistan was preferencing communist militants instead of islamic fundamentalists, would the US have still worked with them against the Soviets? Doubtful, but also the culpability for what came after would have been the same regardless.

The US thought that there was going to be an intervention by the Soviet Union, and considered frustrating that aim to be worth the risk that it might not happen.

I'm pretty sure this is exactly my point (your phrasing makes it a little ambiguous).