@maxdancona,
There is no uniform definition of extremism.
I share this opinion:
Extremism rejects the democratic constitutional state and its values. It disregards human dignity and the rule of law - and often shows a willingness to use violence.
Extremists or extremist-oriented individuals are, for example, against the (respective) constitution, against democratic institutions and the free press.
Extremism threatens the free democratic basic order.
Accordingly, it is a term of demarcation and a negative definition - constitutive for the understanding is the rejection of the norms and rules of the democratic constitutional state.