President Donald Trump’s threat to label anti-fascism protest movement Antifa a terrorist organization has prompted a backlash in Germany, where thousands of social media users have pledged solidarity with the group.

Trump tweeted on Saturday that the activist group was made up of “gutless Radical Left Wack Jobs who go around hitting (only non-fighters) people over the heads with baseball bats.” He said a move was being considered to label the movement a “major Organization of Terror (along with MS-13 & others),” referring to the international criminal gang the Mara Salvatrucha.

His tweet followed the introduction of a resolution by Republican Sens. Ted Cruz and Bill Cassidy, aiming to have the group identified as “domestic terrorists.”

But the call prompted a flurry of tweets in the US and in Germany, where #IchBinAntifa — I am Antifa — started trending on Twitter.