Please read the Communist Manifesto before you lambast it with an uninformed critique.
It's utterly predictable, mostly because we've seen so many try to apply it and fail in exactly the same way each time. We're well past the point where we can say the Communist Manifesto directly leads to dictatorial regimes. I will recant this statement when someone manages to apply it without turning into a dictatorial regime, but don't hold your breath for that.
Now were I disagree with Marxism is the advocation of the "Dictatorship of the proletariat" which I believe results in these state capitalist dictatorial regimes. I'm not an intellectual, don't take my work for it. Chomsky is a good source of information regarding the Soviet Union: http://youtu.be/K4Tq4VE8eHQ
In fact, the Soviets were constantly justifying their policies based on the writings of Marx and Lennon.
No true Scotsman is an informal logical fallacy, an ad hoc attempt to retain an unreasoned assertion.[1] When faced with a counterexample to a universal claim, rather than denying the counterexample or rejecting the original universal claim, this fallacy modifies the subject of the assertion to exclude the specific case or others like it by rhetoric, without reference to any specific objective rule.
The key part is "without reference to any specific objective rule", which I don't think you're taking into account.
I can't do the same for most other ideologies; there's no Conservative Manifesto as it were.
With that in mind we can take Marx's book and compare it against history in these countries. If you do this then you will come to the conclusion that these regimes were not Marxist and in fact not even close to socialism.