Veganism and materialism

If that’s the case, then my point the he has the wrong syllogism still stands

I'm not arguing that the OP's syllogism is perfectly constructed, I'm arguing against your critique of it because I don't think it's valid either.

Well, that’s debatable but it’s not the subject here. Consciousness being a part of material reality is more of a belief than a fact

This is plain Idealism, and it's something that's demonstrably, scientifically false. We as Marxists are dialectical materialist and reject Idealist interpretations of reality. That is the broader problem in your comment, which probably I should have stated directly in my first reply. Your base assumptions here lead you to argue from and for an idealist position which is not compatible with Marxism, and in many cases in general goes counter to reality.

whatever the answer is I think it’s totally irrelevant to the way we live and it’s just mental masturbation

This is also false. The philosophy we take as the basis of our entire worldview has large effects on how we live our lives, especially with regard to political theory and practice. This is the whole point of Marxism and the scientific communist movement. It's the basis on which Marxism is uniquely differentiated from other political ideologies like Liberalism or Anarchism, and it's the reason for it's wide success both in theory and practice.

just the same way we placed white men above women and black people for a very long time

The reasons we did, and still do, these things are material and primarily stem from our material conditions in various historical situations. The reasons these are improving are because the oppressed classes are gaining ground through class struggle. The material reality is changing which is affecting the way our ideology changes, not the other way around. Societies don't become less racist or sexist because they just decide it's morally wrong, changes in the material conditions improve the social and economic standing of these groups which in turn enables the societal changes in what's considered moral. This is achieved by the political struggle of these and related groups.

let’s not forget that we humans are emotional creatures first It’s no coincidence if every propaganda (even Marxist one) relies on emotional and not rational appeal

I would not agree that we are emotional creatures first, as that view disregards the material basis of our emotions. Our emotions are not disconnected from our material reality and we are not as irrational as you suppose. We are complex social beings and a multiplicity of factors go into forming our ideologies, however, the material conditions play a large and primary role, as is taught by Marxist theory, and demonstrated in Marxist practice. People do come to Marxism for moral reasons, but successful practice which results in long term material gain for the oppressed classes comes from a dialectical materialist understanding and analysis of concrete historical situations. The basis and substance of our movements is material, we don't preach morality and focus on choices of individuals. Marxist propaganda, even if it incorporates emotional appeals, is still grounded in material analysis and is expressed as such.

the number of people who will be concerned for moral reasons by the exploitation of animals will grow exponentially

You cannot know what will happen in the future, especially once a communist society is achieved. In any case, this is not an argument that can affect our current reality.

since there is no material reason to support it

This is also patently not true, people that eat meat benefit from eating it, similarly how even the poor proletarians in the West still do benefit from the imperialism conducted by their countries. Of course, in the grand scheme of things, especially environmentally, our current modes of animal farming are unsustainable and destructive and need to be radically changed, but there are reasons that most people today still eat meat. No real change will come about from preaching to consumers about their individual choices, especially in the current system. We do benefit from exploiting animals as we receive food and other products fairly cheaply and abundantly, not to mention the economic benefits of the bourgeoisie which owns the meat industry. To effectively challenge and change this, we should focus on the production side with a concrete materialist analysis, and not form our strategy around the moral condemnation or praise of individual consumer choices. There is nothing wrong with being vegan for moral reasons, but it alone doesn't inform practice and offer concrete practical solution to the problem of capitalist animal industry.

Nowadays, for example, we largely condemn antisemitism and have laws in place against it, however that wasn't the case throughout even much of the 20th century. The USSR, at the time of its foundation, was the first country to effectively challenge antisemitism and its practices which were common throughout Europe at the time. Lenin and the other Bolshevik leaders made many speeches condemning it and educating the population, in addition with enacting laws against it. Their arguments were focused on the material basis of antisemitism, its roots and effects. The change in attitude in large sections of the entire Western population, not just that of the USSR, was ultimately the result of concrete policies and laws, and the spread of education to counter the material realities of antisemitism which was primarily done in the socialist world, but spread to the capitalist West in certain ways. Similar things happened with many other social aspects we now take for granted. With the current decline of material conditions in the West we see a resurgence of antisemitism, and especially sinophobia, which is a manifestation of the same phenomenon. The point is that it is very difficult, if not impossible to change peoples' positions on issues which align with their material interests with moral arguments alone.

Well, calling that chauvinistic is needlessly aggressive, especially in the abscence of any kind of argumentation.

It's not aggressive, I'm not calling it chauvinistic as a personal attack against you, it's just my critique of your statement with, in fact, argumentation provided. Equating the positions of oppressed human groups with our treatment of animals and subsequently preaching, on equal ground, that all are absolutely bad is the definition of chauvinism, especially when those human groups are still oppressed with disastrous consequences in many situations. In my view this is sort of similar to the "all lives matter" arguments. Expanding on the argument - taking our western views and morality (which is largely influenced by our privileged material position in the world) and supposing that it's the clearly correct solution everywhere and that everyone should abide by our standards is by definition chauvinistic. A widespread example are the excuses provided for the "human-rights" imperialism perpetrated by the West all over the world. Socialists are, of course, not a priori removed from this, as evidenced by conflicts between socialist states and the chauvinistic views taken in such cases by the stronger socialist powers in relation to the weaker ones, informed by national interests while ignoring the specificity of each country's conditions. This again highlights the weakness and small scope by which the moral arguments against any such position are limited. If we instead use material analysis of concrete situations in their proper context, we can identify problems particular only to specific situations and find local solution to them. A one size fits all solution is not the answer, as demonstrated, for example, by the differences in socialist construction in different countries around the world.