I think there has to be some basic rules to art, it cant literally be anything and everything, otherwise it's nothing. Like it has to involve inspiration in some way.

Work is not art.

I think there actually is some merit in debating what is art, but we can start by clarifying anything where someone created something with the intent of expressing themselves is definitively art.

This might be a controversial take, but I don't actually buy that Marxism is some sort of antithesis to fascism. They're very much opposing forces in theory, but then again so is liberalism.

Fascism is not fundamentally about being illiberal or anti-communist, but it always is. It is about hijacking a system to enforce an ultimate hierarchy of might make right. Words, ideologies, principles of political philosophy are all meaningless tools to accomplish the fascists true goals. They only want power at the expense of others to the maximum extent. They want to enforce through violence a world where they reign over the infidels, the poor, the weak, the other They'll eventually exterminate those at the bottom, sometimes quickly, but definitely eventually.

Communist states are probably harder to hijack than liberal ones as they require slightly different tactics, but it can happen anywhere. So long as the good ideals and principles that supposedly represent a nation are abandoned, any state can become fascist.

What this ultimately means for your friend is that either they are at risk of co-signing some terrible shit, or they don't actually hate modern art as much as you think they do. It might be that they are more vocal about their dislike, but still respect that people find value in it.

This meme noticeably ignores Socialist Realism which continued to be popular post ww2, socialist cultural influences didn't really fall out of popularity until the cold war shit fully took hold.