You mean the one prior to serfdom?
Yes.
That is even more false. Because slavery was not abandoned during the serfdom era, nor after it.
Correct. However, it was abandoned
as the main mode of production in late antiquity, being replaced by serfdom and the feudal mode of production. It did not disappear entirely, as you stated, and indeed it enjoyed a resurgence in the early Modern period with the slave trade out of Africa. However, in the European heartlands, it remained marginal and lasted only a couple of centuries in the American colonies, where it was introduced and became the main mode of production because the shortage of labour in the colonies. When one mode of production displaces another, the old mode of production never entirely vanishes. There are still cases of slavery in Britain even now, with foreign domestics and sex workers; however, these are isolated cases and not the main mode of economic production.
The fallacy is that they were not hindering its development but instead protecting it, in the case of Byzantium(ie the Latin and Venetian merchant expropriations were the most loud manifestations of bourgoisie dictatorship, and the merchant legalistic treaties signed with the Rus' another manifestation) and the Islamic caliphate was another full-blown capitalist economy.
Trading is not identical with capitalism. And the Islamic Caliphate was
not "a full-blown capitalist economy". They allowed and encouraged trading, but by this standard ancient Rome was a "full-blown capitalist economy". This is nonsense, on the same level as those American pro-capitalists on this forum who try to claim that capitalism is the only "natural" economic system since it has existed since the Stone Age.
The problem with marxist materialism, is that it is greatly underdeveloped, and generalized a lot in terms of geography.
How so? Could you give some examples of this deficiency?
Another fallacy is the assumtpion that the laws were different, the Laws have been exactly the same from the day of the established Constitution in Athens by Solon, which in effect created capitalism in Europe, until today, with very minor modifications, systemized in Roman Law, which has been the Laws of Europe(and lately of many others too) from the antiquity untill today.
Then how do you explain why industrial capitalism first developed in Britain, which
never adopted Roman law? And ancient Athens was
not a capitalist economy; they had
real slaves doing all the work, not just "wage slaves".
"Politics is the art of looking for trouble, finding it everywhere, diagnosing it incorrectly and applying the wrong remedies." - Marx (Groucho)