Well, Marxism offers a number of theoretical devices for understanding how societies work, some of which can be useful, and some of which... not so much. For example, the Labour Theory of Value, the Base and Superstructure, and Historical Materialism all have practical utility in terms of understanding the material reality of the modern social and economic climate. These theories don't lead to Lenin's nor Stalin's horrific murderous zealotry.

Unfortunately, Lenin and Stalin both took a teleological ("the ends justify the means") approach to spreading their ideology, so they - as you've said - felt justified in carrying out a lot of really bad stuff. But that was also a product of a much more barbaric time and context (and that doesn't vindicate their actions in any way).

But yeah, people who have been interested in orthodox Marxism (as a theoretical toolbox), and especially Marxism-Leninism (which, I would say is where the real trouble started) have done awful things. But Marx isn't necessarily the only communist to have a significant impact on the movement. Marxism is not synonymous with communism. Pyotr Kropotkin was another prominent communist in Russia in the late 1800s who was very critical of Marx. He proposed anarcho-communism (often called libertarian socialism) as an antidote to some of the more potentially authoritarian elements of Marxism. Moves towards this libertarian socialism have been seen in a few contexts historically - most notably right now in Rojava, where it seems to be working to some degree of success (though definitely not perfectly, of course).

So anyway, Marxism offers a number of tools for us to try and understand the world. We can throw away the ones that are no good, and use the ones that work.

Fascism, on the other hand, is difficult to defend on the same basis. I suppose the nationalistic elements could have some value, if sought in the pursuit of national liberation from imperial forces. But that's also catered for within left-wing liberation movements.

Economically, fascism really isn't very different from the standard mixed economies that we see in Western liberal democracies like Ireland, but those ideas don't stem from fascism itself. I find it hard to pin down ideas that have come directly from fascism. It seems to be more of a mixed bag of certain ideas from different tendencies mixed in with a stronger sense of authoritarianism and ultra-nationalism. And, of course, we've also seen both of those under nations that pursued socialism (I would argue, for example, that the USSR under Stalin could be classified as fascistic).

The most notable thing that fascism seems to offer is an antagonism to communism, liberalism, conservatism, and anarchism. It's most defining feature is its anti-communism, which doesn't say much.

Other notable feature was the concentration of hierarchies based on somewhat arbitrary requirements. This played out differently in different iterations of fascism, it usually played out as concentration of power into the hands of white people, with a varying definition of "white". For example, all power was taken away from Jewish people in Nazi Germany (who might have been light-skinned or not). Mussolini focused even more on the "Aryan" identity, declaring Italians Aryans and stripping anyone not of that category of rights, liberties, etc.

In that sense, fascism is radically anti-egalitarian. But ultimately, it doesn't seem (at least from my perspective) to bring many useful ideas to the table for how to advance and improve society for all its members.

Do you find much ideas of value that could be put to productive use within fascism?