I wasn't aware that there was a credible argument? Marxism (or to keep it simple, anything further left than democratic socialism) has failed utterly everywhere it was attempted, being the root cause of misery, tyranny and many tens of millions of deaths. I wouldn't deny the attractiveness of theory but unfortunately it doesn't survive first contact with human nature.
Having read a little bit on Marx and his theories, I'd be interested to know where they've been tried out.
Waitrose is the closest example I can think of.
I'd like to think that Marx has a little chuckle at that one.
The most shamelessly (upper)/middle class retailer in the country with its Marxist principles.