The left-right political spectrum is not so useful given the diversity and disparity of modern political systems. Socialism and Fascism are in no conceivable way incompatible. They are not opposites. Indeed the peculiar character of true socialism lends itself startlingly well to fascist ideals.
Fascism is the political ideology that states society is at its strongest, and ergo its best, when all people work together. There is an old Roman metaphor that people are like twigs, scattered on the ground they may be easily trampled, but bound tightly together in a bundle they are strong and may resist outside threats. Fascism tends to marginalize minority opinions, and are known to promote nationalism or racism as fundamental to societal unity. Fascist states also tend to be preoccupied with fear of citizen uprisings, and often employ propaganda and domestic surveillance to ensure a population remains within a docile-supportive range.
Socialism is an economic system whereby the government takes ownership of the means of production. The means are then leased back to the people with the oversight of government to ensure the best use of a society's resources. Socialism may either give the means of control over to a democratic body that takes the opinions of the people into account when planning the economy, or to a body like the Communist Party in Soviet Russia, a fascist group if ever there was one.
Fascism = one party, or as the Germans so eloquently put it: Ein Volk, ein Reich, ein Fuhrer!
Socialism = the government owns the means of production, all citizens are government workers
Marx said that after capitalism gorged itself into ruination, it would be replaced by socialism. In other words, the people would rise up and regulate the economy to avoid a society in which the creation of a bourgeois class was institutionally inevitable. His description was an oversimplification, with the government outright owning the means of production rather than merely regulating corporate practice, of what is going on in modern day Europe.
Marx said nothing about the structure of the government that would own the means of production, the notion of a uniform Communist Party was an addition made by Lenin and, to a greater extent, Stalin. It is from Stalin that we get the concept of "political correctness," which is Joe's day meant the most rigorous and logical interpretation or application of the writings of Marx and other Communist dogma.
Anyway, poli-sci lecture over, I just want to attempt to clarify the essential truth you have hit upon with more precise language.
Fanaticism may dress in many different suits, but it always smells like bullshit.