Interesting spin. A communist group in Afghanistan held a coup and then called themselves a government. To protect themselves from those they deposed fighting back, the coup leaders asked for help from the Soviets.
Actually, no, that's not what happened.
"On 27 April 1978, a coup staged by the People’s Democratic Party (PDP) overthrew the government of Mohammad Daoud. Daoud, five years earlier, had overthrown the monarchy and established a republic, although he himself was a member of the royal family. He had been supported by the left in this endeavor, but it turned out that Daoud’s royal blood was thicker than his progressive water. When the Daoud regime had a PDP leader killed, arrested the rest of the leadership, and purged hundreds of suspected party sympathizers from government posts, the PDP, aided by its supporters in the army, revolted and took power."
What did you expect the PDP to do, stand by and watch their comrades slaughtered and jailed, the republic turned into an autocracy by an opportunist who received overtures from the US?
"Daoud gradually broke off his alliance with the PDP, announcing that he would start his own party and ban all other political activity under a projected new constitution."
They were part of the government in the first place, and had every right to overthrow Daoud.