“Communism bad”
“Why?”
200 year old tropes so ancient they were debunked by Marx himself
Of course, you go through the motions of explaining the most basic political concepts that could be grasped by skimming the cliff notes for literally any Marxist works
“Friedrich Engels? Is he like the president of Germany or something?”
It’s like a kindergartener trying to teach you calculus.
You're correct that the big majority of philosophy academics are liberal. It's good to bear in mind tho imo that philosophy professors are not the only people employed as philosophy educators or teachers and are far from the only people who have seriously studied philosophy, formally or informally. There are a decent number of Marxist philosophy PhD's, not least from the combination of their experience of the labor market and the fact that they've had the time or priviledge to think critically about and 'deconstruct' certain key concepts that are essential parts of capitalist/liberal ideology.
The issue is not so much, imo, in areas of philosophy like philosophy of science, mathematics, language, logic or even epistemology and metaphysics. The more immediate issue is when it comes to areas like moral or political philosophy, or philosophy of economics. The biases in these latter cases are really evident and you are correct imo that when considering that social function they are largely serving as more sophicated mechanisms of ideological legitimation of liberalism or reformism. E.g. any western political philosophy department is going to be dominated by Rawlsians, i.e. the least politically relevant and most mind-numbingly boring political theory that was ever shat over the face of the earth. The most recent wave of Rawlsian thought is soc-dem in nature, looking at his late texts on 'property-owning democracy', meaning accepts to have soc-dem societies which 'socialism' has been reached by reform but in which there is still private property. Obviously even a slight understanding of Marxist theory dispells this idea as obviously incoherent. The reason it is still present is because it acts as a moral paliative that petit-bourgeois soc-dem intellectuals - who are intelligent enough to realise that contemporary capitalism is completely fucked up but are neither intellectually sophicated enough nor morally strong enough to correctly diagnose it or offer genuine solutions - can use to sooth their consciences.
That being said, you do often see a correlation with how deeply or seriously people are interested in philosophy and their interest in Marxism. The danger is that these people are often simply intellectual Marxists or Marxians with an abstract idea of politics. This is generally far from being entirely their fault, but it is a danger. In practice they are often interested more in abstract argument about certain ideas as opposed to the empirical and historical adequacy of Marxism as a theory of social reality.
Right! This is a criticism of philosophy in general, and I think it's very well-founded. In particular, the incentive structure of professional philosophy tends to encourage this kind of abstract theorizing that's disconnected from real-world social ills. Any kind of "applied" philosophy (applied ethics, applied political theory, philosophy of any particular science, &c.) is very much treated as a kind of second-class research project within the profession, and inferior to "pure" metaphysics & epistemology. My own area of specialization, foundations of climate science, is no exception here: making contact with concrete problems, or engaging with actual scientific work, is always seen as less prestigious than working on pure logic-chopping abstract theories.
I do think you're right that you're not incredibly likely to find "practicing" Marxists at the upper echelons of tenured R1 philosophy (though there are a few prominent exceptions that I'm aware of, and it still seems a bit more common than it is in most other disciplines). However, there's a vast underclass of (let's say) lumpenprofessoriat members–adjuncts, community college professors, non-tenured lecturers, and so on–that is, in my experience, extremely likely to endorse and be engaged with Marxist thought. As you say, this is almost certainly down to material conditions, at least to a great extent. I do think that a background in philosophical reasoning can help with  though.
Yeah it does seem to me that philosophy department's and the imposition of 'publish-or-perish' culture there (in a place where that makes possibly the least sense), compounds the issue of people starting their careers as academics and searching from a cottage-industry to milk for the sake of publishing; which is obviously not the kind of environment where philosophy will best do it's actual job of helping to dialectically clarify and conceptually develop the other areas of science, ethics, politics and aesthetics (in collaboration with these fields obvs). There are exceptions but they are still only exceptions which prove the rule imo.
Yeh the lumpen-intelligentsia has far more Marxists in it (as you can see on this site) than many or even most current demographics in many societies, which is interesting as they are now the large majority of actual workers in higher education and yet remain largely invisible.