It would probably trigger more debate if the link you referred to actually explained this thesis more convincingly rather than focus on the often deplorable language.

E.g. the oft denounced 'On the Jewish Question' that is predictably cited in your link is a work arguing for the political emancipation of Jewish people.

It does so with language that is offensive to a modern reader by turning around and mocking the arguments used by Bruno Bauer who argued against political emancipation.

That [use of language] makes it problematic, and I wouldn't recommend it to someone without commentary on the polemical debate it was a part of.

But Marx is addressing and attacking the very kind of political oppression of Jewish people that forced his father to convert to Lutheranism - which the article of course mentioned without later citing its relevance to 'On the Jewish Question' -, making the point that Jewish people should have political rights without being forced to abandon their religion.

As evidence of Marx willingness to use now-unacceptable language, it works. As evidence that he hated Jews it's a massive own goal for the article writer to use an article that argued for expanding Jewish peoples rights.

There are many legitimate criticisms to level against Marx' language. But this article is dishonest or ignorant in it's presentation of a lot of it.

To address specifically the Communist Manifesto, suggesting it is talking of a conspiracy suggests you have not read it, or understood it. If anything one of the key aspects of Marxist thinking was to directly denounce the idea that the individual actions of a few have much - if any - impact on history, and to present a conception of the way society changes as one controlled by historical and economical necessity, inevitably developing based on market forces.

The idea of capitalism as a conspiracy runs directly counter to the Marxist idea of historical materialism, so it's bizarre to try to frame his work as promoting a conspiracy theory.

Furthermore, the whole first chapter is fan-boy level praise for capitalism as having brought humanity to a level of development not seen before, and for how the free market is the "battering ram" that over time forces even the worst bigots to drop xenophobia, driven by economic forces.

If he was promoting a conspiracy, he was speaking awfully well about the supposed conspirators, given the idea of the development of new modes of production as the wheel of progress is a central thesis of Marxist thought, and his insistence that socialism/communism is a necessary consequence of capitalism rests on the idea that economic progress is inevitable and detached from the actions of individuals.

The Communist Manifesto presents capitalism as a huge step forward, just still flawed and something that would eventually give way to another step forwards.

This idea of Marx as promoting a conspiracy is an inherent demonstration of a lack of understanding of Marx writing, because it lifts up the idea of great leaders where Marx consistently put that idea down and criticised it, by talking of whole movements in terms of forces and modes of production within which the individuals - even the capitalists themselves - are trapped and playing out a role they have little control over.