Every liberal does it too, from center right radlibs to far-right "conservatives": the most extreme right fringe liberals hate the mainstream liberals for not being bigoted enough, the mainstream libs hate the radlibs for not being cruel enough, and the radlibs hate the left for not being chauvinist enough.
Denouncing chauvinism in particular is like a liberal moral event horizon, a cardinal sin against their self-interested belief in the righteousness of the imperial hegemon that keeps the treats flowing at gunpoint.
What's the proof of this?
Every engaged political actor does this. There's no material benefit to being a leftist in the west, but it does feel good living by your principles. Liberals simply don't share the same principles, they aren't secretly thinking they are morally inferior or whatever.
I disagree somewhat. If we're to believe this map posted further up in the thread, any average person who does not live in one of the blue countries would benefit from global communism:
The US, Germany, the Nordics, and most of eastern Europe is a large portion of the West's population.
I think that how this potential benefit is weighed against the real possibility of sacrificing one's life, and potentially entire communities, for a revolutionary cause, instead of simply staying out of trouble and trying to survive, is the more challenging and important issue than a lack of class interest in socialism.
Even in the blue countries, the possibility of living an unalienated life with meaningful control over one's work, community, and society could be more appealing in the abstract for many than simply making more money in a rotten, alienating system. There's more benefit in socialism than simply meeting one's basic needs, as important as that is. The problem for anyone is actually working towards a point where that possibility becomes real. That entails danger and instability.
Good points, in the long term communism does materially benefit most people. And there is some benefits in the current day to be a leftist in the west, like being part of a community and finding meaning in life beyond the market.