Simply because communism is that way. It is a thought, an infiltration in the mind of the weak. They sway the weak and powerless, and in turn, the weak and powerless play on the good nature of the of the righteous. That is how communism gets a foothold in society. But mark my words, communism is best dealt with at the end of a musket. They do not just go away. They will slink into the shadows, awaiting their next opportunity to infect the minds of the weak and start all over again. If freedom is your values, then communism is best exterminated on contact.