Tbf extremism itself isn't wrong. Any perspective can be considered extreme if it is too different from the status quo. Different isn't necessarily bad.
Granted religious extremism is typically far right reactionary ideology which is bad so I'm not really defending it. However, I find that a lot of people, especially Americans, call anything that radically challenges the current system extreme and therefore bad.
The same can be said about religion. Less than 20% of Americans identify as Atheist or Agnostic, the far right extremists do not have support from 80% of the population.