It’s amazing—and horrifying—what can happen when people have mushy-headed, vague beliefs in their heads, lacking what I refer to as “clarity of thought.” 

I agree with you here, but I also think that you are twisting your arguments a bit so that they can fit your conclusion better.

 “Everyone should have the necessities of life,”  “Those who can afford to help others, should” 

I don't think  Marx  had any idea how others would interpret his words and he also probably lacked an understanding of human nature(I'm an optimist).

 “From each according to his ability, to each according to his need.” 

I think this assumes that everyone would know what his own abilities and needs are(and would act accordingly).That's not realistic at all.

 When a communist says it, they mean “the rich should be forced to give to the less fortunate.” 

Here you are generalizing and from should it became similar to must. It's not the idea or the philosophy that is   somehow "evil ". It's just that it's naive and assumes a set of conditions that don't exist. People just aren't ready for such an idealistic way of living. Of course anything that is enforced becomes ugly.

Suppose you created the idea of voluntarism. And then a lot of people liked it and got exited about it, then twisted it when it suited them and started enforcing it(totally contrary to the core idea). I guarantee you wouldnt like the result.

Basically what I'm trying to say is that there is no perfect government or system. It all depends on the individuals.If the individuals are mature enough any government system would work even monarchy or dictatorship.