"Terrorist" and "extremist" is the way the Russian government refers to the opposition. By labeling them in this way, it prevents any civic anger in case a member of the Russian opposition is jailed, beaten or murdered. It's scary when your government labels you as someone who has to be exterminated, but we choose to make art about it, instead of simply being afraid.

Russian text (text in circles quotes Pussy Riot's song "Putin Has Pissed Himself" that they performed in January 2012 on the Red Square):

circle (big font): свобода протеста мы существуем райот райот выйди на улицу
circle (small font): выйди на улицу живи на красной покажи свободу гражданской злости
upper text on the balaclava: TRR☦️ST
lower text on the balaclava: ЭКСТРЕМИСТ

English translation:

circle (big font): the freedom of riot we exist riot riot go to the streets
circle (small font): Come out, Live in the Red, Show freedom, Civic anger.
upper text on the balaclava: TRR☦️ST
lower text on the balaclava: EXTREMIST