Except when it came to economics, something that Marx heavily criticized him for. Instead of anarchists adopting Marxist economic theory, they decide that they'll just ignore it, because reasons.
No, just doing that doesn't make you an empiricist if you have the wrong form of analysis.
I'm not the one that brought her up. An anarchist did, and I told him she didn't mean shit and wasn't comparable to Rosa Luxemburg.
Not accepting Marxist theory is rejecting science. Anarchists do this, therefore they are not scientific socialists. It is one thing to critique Marx and refine the theory. It's another to claim that it's "authoritarian" and reject it outright.
The first is true, the second is not something I've ever seen anyone claim. Communism is far different from socialism and Marx never claimed anything but that. So maybe those "Marxists" need to read more Marx.
It's not about patting yourself on the back, but if we agree that materialism is true, and that we can rightfully arrive at correct conclusions through the scientific method, then it only follows that economic theory should also be based on science and nothing but in order to see what the right step is forward. Now, that is not to say that science compels us to be socialists, but rather that if we already have values that tend this way, then we must use science to build socialism. Failing to do this is meaningless and a waste of time.
Proudhon made a couple of mentions of it, and we don't know what he would have thought after Marx came to prominence. If he truly was a scientific socialist, he would have become a Marxist, since that's where the real meat and potatoes are as far as scientific theory is concerned. Now, maybe Proudhon would have written much about economics and made real-world testable predictions, but he did not do this, and using a term, does not a scientist make. Evolution was coined before Darwin, and yet Darwin is credited with the origin of the theory because instead of just wondering, he went out and did the work to build a working theory. Marx is the same way.