Piggybacking on the post complaining about strange things Americans believe.
To me, Marx's belief that real socialism incorporates a materialism that disdains everything that's not concrete is a mistake that doesn't reflect the origins of the socialist movement. If you look at early socialists like Fourier, Proudhon, and Louis Blanc, their ideas contain reactions against French materialism combined with an ideal of social justice formed by criticism of free market Enlightenment thought. Not everyone shared Marx's opinion that bourgeois society was progressive because it created a new, rational, order.
Early socialist thinkers were sympathetic to the goals and ideals of the French Revolution and the Enlightenment, but they didn't believe that materialism was sufficient to guarantee a good life and a just society. Life was more complicated than atoms bumping into each other, and the idea that human life resembled the interaction of billiard balls devalued the human condition and mowed down the ambiguities and subtleties inherent in life.
In fact, to assert that the Social, that society, is real and important in a non-rhetorical sense was to reject a key notion of materialist philosophy: the ultimate self sufficiency and autonomy of the individual. Enlightenment thinkers like John Locke, for instance, John Locke, denied the idea that the Social and Society are valid categories in and of themselves. Because of this, and their criticism of materialism, the early socialists were a type of Romantic, and are sometimes referred to as Romantic socialists. Like the Romantics they wanted to re-orient the world to what was not immediately tangible, philosophy notwithstanding. In the socialists' case they focused on social relationships instead of subjective experience.
As a reflection of their skepticism about materialist individualism, the early Romantic socialists were also in harmony with liberal nationalism. Liberal nationalists were not reactionary but wanted to assert their autonomy and cultural uniqueness in the face of non-democratic mono-cultural regimes. Isaiah Berlin argues in "The Roots of Romanticism" that they emerged in opposition to Napoleon's exportation of the French enlightenment across Europe, but a different perspective is that it was formed by peoples who benefited under Napoleon who now faced their old, undemocratic, mono-cultural oppressors. The original nationalists in countries such as Poland, Italy, and Hungary agreed with liberal principles, but wanted to implement them in their own way, and retain their own language and culture. The Romantic socialists and the liberal nationalists were the main progressive force in Europe from the turn of the 19th century to the years after 1848.
While Romanticism lead to Wagnerian excess and reaction, to a rancid organicism and ultra-conservative, exclusionary nationalism, that was a later development. Reaction set in when it happened, and the Romantics adopted more and more outlandish views, hardening from liberals to conservatives.
Modernism was not a simple return to Enlightenment values but a restatement of them within a context opened up by Romantic and Idealist criticism. Monistic materialism, for instance, the official doctrine of the Bolshevik party from Plekhanov on, was decidedly unlike classical materialism. It recognized social relationships and that society was more than just a collection of individuals, but it differed from organicist Romanticism in rejecting the idea that society is like a body with different social groups functioning like organs, and that it was in some sense 'alive'. Unfortunately, the socialists of the early 20th century outside of Russia who were dogmatically Marxist either forgot or never learned this.
Despite being active during the height of Romantic socialism, Marx only found his ideological home after the reaction against Romanticism took over. Marx heavily criticized the Romantics, but his criticism preceded the reaction by many years, and was formulated at the height of the movement in documents like the Communist Manifesto, written in 1848. To me, Marx fundamentally misunderstood the positions of the people he criticized and naively sought to turn back the clock to the French Revolution in a post-Hegelian setting. It should be noted that many of the people whom Marx condemned in the Manifesto, like Proudhon and the Fourieristes, had important followings while Marx was still just a journalist. His thought resonated with the Modernist critics of Romanticism, but depended on Hegelian principles that they themselves would come to criticize. Nevertheless, it provided grist for the mill for the less thoughtful in the socialist movement.
By reasserting Enlightenment values in an unthinking manner, these socialists fueled critics who saw the whole movement as crude, absurd, and stupid. After all, the ideas had been criticized for a hundred years ad nauseum, and were now being put forward again as if nothing happened. Despite the subtleties of Modernist philosophy, critics saw the same old problems lurking under the surface, and were afraid that a stupidly Modernist materialism would produce a greater destruction of social life than Enlightenment materialism itself. But the crudeness and insensitivity to aspects of life not reducible to atomic theory by these people was not only unnecessary to socialism but was in some ways counter to the impulses that started it.
I think it's possible for socialism to take the framework of the Modernist context, combine it with a changed Romanticism-- perhaps influenced by the Surrealist project of reinventing the world (a classic Romantic concept in a Modernist framework), and combine all of it with a post-modern sensibility to produce a socialism that meets the needs of the head, the heart, and the body without doing an injustice to any of them.
*on edit: here's an interesting take on Pan-Slavism from Engels in 1849, the year after the Manifesto was published. At the time, the tendency wasn't reactionary, and similar movements had been founded for Italian and German unity.
Neue Rheinische Zeitung February 1849
"We repeat: apart from the Poles, the Russians, and at most the Turkish Slavs, no Slav people has a future, for the simple reason that all the other Slavs lack the primary historical, geographical, political and industrial conditions for independence and viability.
Peoples which have never had a history of their own, which from the time when they achieved the first, most elementary stage of civilization already came under foreign sway, or which were forced to attain the first stage of civilization only by means of a foreign yoke, are not viable and will never be able to achieve any kind of independence.
And that has been the fate of the Austrian Slavs. The Czechs, among whom we would include the Moravians and Slovaks, although they differ in respect of language and history, have never had a history of their own. Bohemia has been chained to Germany since the time of Charles the Great. The Czech nation freed itself momentarily and formed the Great-Moravian state, only immediately to come under subjugation again and for 500 years to be a bill thrown from one to another by Germany, Hungary and Poland. Following that, Bohemia and Moravia passed definitely to Germany and the Slovak regions remained with Hungary. And this historically absolutely non-existent "nation" puts forward claims to independence? "