That is not true. Germany has a long history of extremism and terrorism from the left and right side of the spectrum. The only thing missing is the international context, so there is no war against terror, for example, and the discussion is usually not global since there are no wars to fight in other countries since it's all homemade. Other European countries such as Ireland or Spain have had their fair share of local terrorist groups as well.

More info can be found here, just as examples for Germany:

for the left: https://en.wikipedia.org/wiki/Red_Army_Faction

for the right: https://en.wikipedia.org/wiki/National_Socialist_Underground