good portion of u.s. left probably hadn't paid much attention to popularly received 1978 uprising that brought people's democratic party (pdpa) to power, hadn't taken note of treaty of friendship and assistance that government signed with ussr creating basis for soviet military help, and wasn't familiar with pdpa program of land reform, literacy campaigns, equality for women (abolishing forced marriages & bride sales while granting women right to work), and cultural rights for national minorities...
attempt at 'rapid reform' of countryside generated peasant opposition that was welcomed by reactionary elements and previous ruling interests: wealthy/powerful feudal lords, tribal chieftains, traditional clergy, internal pdpa split destabilized already difficult post-revolutionary situation and made task of moving country from feudalism to modernity even more daunting...
soviet leadership rejected early request for military assistance by afghan government clearly committed to progressive social change, decision to pursue military action was only made following failed attempt to negotiate political settlement that would have created broader coalition gov't and slowed pace of reform and president's murder by supporters of his rival who had apparently sought u.s. help, having met a number of times with then-u.s. ambassador...
one didn't have to 'hail the red army', but one should have been able to see that carter would use afghan situation to justify policies already being prepared - way truman used greece & korea and johnson used gulf of tonkin, left anti-communism in US was pervasive enough, however, to prevent many from accepting that soviets were trying to bring order to chaotic situation in neighboring country *and* trying to prevent setback for forces of socialism (even if it was socialism made under circumstances not chosen but under circumstances directly encountered, given, and transmitted from the past)... mh