I think it is normal and even desirable for young people to be interested in extremist politics. Communism but also anarchy, dictatorships, etc... Modern day "free market" democracies are really a "least bad" system, there are many things wrong with them, things that communism or why not a ruling king can address. In practice, most people discover soon enough that it doesn't work, but to go to that conclusion, you have to at least consider it, and it is better to do that when you are still young and not involved in actual politics.
Also, being able to consider other systems is a sign of a well functioning free country. If any idea other than "democracy is the best" is being suppressed, then it is not really a democracy.