Especially with extremists, you should have a solid foundation of argumentation, because they will not ignore even little fails and weaponize everything against you if necessary.
It's unnecessary: extremists usually aren't seeking to change their mind, and they'd sooner fabricate evidence of a fail than acknowledge The Perfect Argument That Totally Changed My Mind
Especially with extremists, a solid foundation of argumentation will do you no good because the facts are beside the point.