vänsterkid

Etymology
+, i.e. literally left-kid or leftist-kid.

Noun

 * 1)  A young leftist; a young person, often a teenager, with strong left-wing political views and a strong and passionate interest in politics, sometimes at the level of an activist.

Usage notes
The term is almost universally considered a pejorative as the suffix  is meant to imply inexperience, irresponsibility, and inability to use and apply critical thinking. It is mainly used by advocates of right-wing politics to refer to an alleged stereotype of teenagers jumping on the bandwagon by adopting left-wing views.