The communist parties have very low ratings and never make it into coalition governments so they are not a threat. The Greens also have fairly low ratings and despite the image, they tend to be elitist neoliberal types. None of these people or parties are as bad or as dangerous as the AfD which is a party of grifters and fascists, full of unhinged people, who, even if you ignore all the hateful rhetoric, you couldn't trust to not destroy the country economically and politically.