Hmm, well that seems to take the passion out of things.
Surely no moreso than a passionate emotional investment in ecological conservation is precluded by a scientific understanding of the objective forces at work on the ecosystem.
Neverending growth is unsustainable. A healthy capitalism grows at approximately 3% per year. If it's not growing then capitalists aren't doing what the system compels them to do. This would be a paradox, because the capitalists would no longer be capitalists, and so it doesn't happen.
The degree of regulation of capital is cyclical, and is a product of the irreconcilibility of class contradictions. The law of the falling rate of profit determines that it's necessary to increase the rate of exploitation. Accordingly, capitalism brutalises the proletariat, the resulting proletarian struggles win regulations and restraints on capital (programs of class compromise), capitalist logic (the profit incentive, systemic pressures determining bourgeois action) chips away at them, capitalism again brutalises the proletariat, proletarian struggle again ensues, and round and round it goes...
Neither the USSR nor China were ever communist. The Russian Revolution was betrayed and eventually defeated. It didn't implode due to some defective 'communist' logic. The Stalinist bureaucracy became an organ of the international bourgeoisie. The class relations changed, there was an economic revolution, but politically the revolution was betrayed.
And of course neoliberal reforms in China resulted in an increase in the national wealth. It's similar to the process of 'primitive accumulation', which is the drive for capitalists to seek means of exploitation 'outside' of capitalism (land, really). In this case though it's an immense untapped investment market and an as-yet-unexploitated (by capitalists) labour army. I'm not really well up on the specific effects of the Chinese reforms, but I do know there is a lot of lies surrounding it, a lot of spin, both from inside and outside of China, and I do know that the conditions in which the Chinese proletariat and peasantry now live are appalling. The effects of the reintroduction of capitalism to Russia 20 years ago were devastating to the Russian working class. Life expectancy has dropped catastrophically, organised crime, murder, prostitution and homelessness have skyrocketed, etc. I'm not apologising for Stalin or Mao, but the reintroduction of capitalism into degenerated workers' states is not a big success story for anyone but the international bourgeoisie.
This is a complex question. I think that we have to begin with the realisation that the academy is an inherently bourgeois institution. The entire reason that universities exist, from the point of view of the bourgeois state, is to prepare priviliged individuals for competition on the middle-class labour market. It's thus absolutely not in the least bit surprising that in economics and business schools there is a broadly anti-Marxist leaning, and an elevation of neoclassical (pro-capitalist) economic theory, and that out of these schools comes the so-called 'libertarian' worldview. In the 1920s and '30s the neoclassicists engaged in debate with Marxists, but that hardly happens anymore.
And scholars too are subject to systemic pressures to produce a certain kind of thought, and in newly reformed or newly neoliberalised 'communist' societies such pressures are to produce anti-Stalinist thought, and not only that, but also to produce neoliberal/libertarian thought, and of course they, as upwardly mobile middle-class career academics, would have nothing to lose in doing so (that itself is the systemic pressure, there are rewards for producing such thought). And of course the Stalinist state had gone to the greatest imaginable lengths, all throughout its history, to identify itself as the logical and theoretical and moral continuation of Bolshevik Marxism. It was Trotsky who coined the term Stalinism; the Stalinists referred to themselves as Marxist-Leninists. So deep was the Stalinist betrayal of the revolution, it even expertly buried its betrayals, disguising counterrevolution as revolution.
So now the question of the New Left. Following Stalin's 'Year of Terror' in 1937, show trials, purgings, etc, communist parties all over the world suffered internal struggles and splits over whether to denounce or defend history's only successful proletarian revolution and the world's only workers' state. There is no overstating the immensity of the Stalinist blow to the struggle for socialism, it was crippling.
Two things happened in 1940. Trotsky, the last surviving Bolshevik participant in the 1917 revolution was assassinated in Mexico by a Stalinist agent, and two non-Marxists, Theodor Adorno and Max Horkheimer, adopting plenty of Marxist terminology, published
Dialectic of Enlightenment, beginning the school of academic Marxism, ie: critical theory. Critical, not revolutionary. So in 1940 the Russian Revolution was finally stamped out entirely, and the same year the stage was set for what would replace it: a neutered, bourgeois form of Marxism that Lenin had even predicted in the opening passages of
The State and Revolution in 1917. This is the bedrock of the New Left. Most of the world's Marxists are now middle-class career academics, who are subject to systemic pressures to produce a certain kind of thought. No wonder the premium on cleverness over truthfulness. Once a truth is stated it needn't be stated again, but cleverness 'liberated' from the search for truth can go on innovating, books can go on being published, careerists can go on and on up the ladder.
The "ugly reality" you refer to came about under specific and unrepeatable historical conditions due to the betrayal and ultimate defeat of the revolution. It only provides further evidence in support of the soundness of the Marxist theories of capitalism.