Do you think that the retreating Communists' policy to pay for goods they wanted during the Long March was a good idea?
For Communists to propose and adhere to a policy of purchasing goods and services seems to be their ultimate hypocrisy. Far afield from "Each according to his ability; each according to his needs," they embraced certain Western economic principles that granted a certain reverence between supplier and consumer, but which still today strangely remain long-maligned world-wide.
It was a peoples' army, made up almost exclusively of the Chinese peasantry. It only made sense, both practically and philosophically, that every effort would be made to maintain the support of the people in any way possible. It also made it clear, rightly or wrongly, that the communists were fighting "for the people", and this was a pretty powerful message among a population that had suffered greatly at the hands of warlords and dictators.
As others have pointed out, it was a very smart move of the Communists to pay for goods. They recognised that their weakened position meant that they needed the goodwill of the people. If they had to face the opposition in addition to a disgruntled populace from which they were robbing, it could have been a very different story.
Yes. Any time there is war, there is discontent and malice. People don't really need much reason to channel that malice toward the government when they are hungry, cold, improperly housed and clothed. If the troops had stolen or seized the goods they needed instead of paying the people from them, there would have been war on two fronts--at home and abroad.