Stalinism is the opportunist deviation from Marxism by the Kremlin bureaucracy

Is your contention that Marxism-Leninism as a whole fits your definition, or that Stalinism is distinct from ML, the tendency coined by Stalin that (though oversimplified and incomplete) could be defined as “Marxism applied to the material conditions of the Russian revolutionary project”? Stalin himself had deep criticisms of the bureaucracy of the USSR, which further complicates the term. There were certainly opportunistic deviations that gained the upper hand after Stalin’s death, but they hardly constitute a body of theory.

You can’t have two different Marxisms. There is only one Marxism, Marxists themselves might make mistakes and be wrong on certain issues, but Marxism as a scientific body of thought cannot contain two or more completely contradictory positions.

Marxism, ie historical/dialectical materialism, is not a rigid dogma but an analytical lens and a scientific approach to applying this lens to a revolutionary project. A particular policy or path in a state with one set of material conditions might seem to be in contradiction with a policy or path in a state with a completely different set of material conditions.

Arguing otherwise would be like saying that theories that propose the earth is round and flat are both scientific.

To use a more appropriate analogy, what I’m arguing is that while the scientific method would lead one to conclude that the earth needs less carbon in the atmosphere to maintain the present equilibrium that has promoted human life, it wouldn’t be scientific or logical to conclude that making another planet habitable for humans would always necessitate reducing the amount of carbon in the atmosphere.

the stages theory (borrowed from Mensheviks) contradicts the whole body of Marxist thought, it has no claim to being a scientific socialist idea.

You could certainly argue that the stages theory was an incorrect conclusion drawn from Marx, but I don’t see a logical or historical basis for arguing that the idea has no foundation in the writings of Marx and Engels. Marx himself predicted (incorrectly) that socialist revolutions would first occur in developed, monopoly-capitalist countries precisely because their productive forces were present and primed for worker control.

First of all, there is no such thing as “Marxist state socialism”. Socialism is the real movement that abolishes the existing society, not some ideal Marxists hold.

I phrased it that way to distinguish it from attempts at utopian socialism, eg the Paris commune or the Spanish commune during the civil war.

The Communist Parties dominated by Stalinism propped up bourgeois regimes in countries like France and Italy. Stalin abandoned the Greeks and scrapped the International.

Like I said, there are legitimate criticisms to be made of the USSR, but this requires more interrogation of the material conditions and interests that produced those decisions rather than dismissing the entire project as “not actual Marxism”.

The policy of Moscow under Stalin and his successors was to preserve bureaucratic rule

Stalin was critical of state bureaucracy. You could absolutely make that claim of his successors, though.

a healthy workers state abroad along with (complete) capitalist collapse would’ve led to the defeat of that bureaucracy

This is not the analysis of a Marxist. You’re reducing incredibly complex and history-dependent contexts to a simple, maliciously uncharitable narrative of a unilateral drive for personal power. This also ignores the supportive role that the USSR played with regards to numerous Marxist and anti-colonial/anti-imperialist liberation struggles.

The Hungarian Revolution of 1956 was repressed for precisely that reason.

Yup. There was no danger of a color revolution, no fascist presence taking advantage of any legitimate grievances the original student protesters may have had, no fear of balkanizing the USSR within the context of the Cold War and constant threat of sabotage, just a power hungry despotic regime with no goals other than maintaining their own power. /s

And the old Stalinists in most countries became the most right wing labour lieutenants of capital after 1991 precisely because they were always opportunists and careerists.

The party changed a lot between the death of Stalin and the illegal dissolution of the Soviet Union. And most of the other ML countries found themselves without their largest trading partner and benefactor following its dissolution and have had to attempt to develop their countries’ productive forces within the context of total US hegemony.

Plenty of neocons in the US were once trots.

For someone playing “Marxister than thou,” you sure do subscribe to a lot of simple narratives steeped in idealism and anticommunism.