I don't know if I would say as dangerous, but that may just be caused by how it's in Denmark (and most western countries).
Nationalists (and those who are worse) usually tries to divide the people, which creates a lot of anger.
Even though communist extremes exist (also in Denmark, though they are very few), but they don't seem to create the same anger.
But of course, in countries where communism is still big, it is absolutely a threat as well.
We have a semi-communist country, but other than being terrible at economics, I don't see them as much of a threat.