It was no more forced on them than the original annexation of the country and colonization of France.  You do realize that North Vietnamese are Vietnamese, right?

I do go to China a lot and have many friends and business acquaintances there who lived through the Mao/Chang upheaval.  They'll tell you that when China went the Mao route, it was expected since much of the country was dirt poor at the time and wanted the government to bring them out of starvation and poverty.  Now, whether it still fits well for them is their choosing.  No, not all China wanted it.  But, it's the way things worked out since the "right" people at the time did.  And, you'd be surprised how much freedom people have in China, especially in business.