Those two questions are only somewhat related. The question "should we ban an undemocratic party that wants to work against core values of our constitution" has only become really pressing because the current government is so unpopular. The actual reasoning for or against the ban do not relate to the popularity of the government.

Taking the current state of affairs and concluding that voting enemies of the constitution into the government would be the solution is not something the majority has to accept as a valid political point of view.

You may call that antidemocratic but there are good reasons we have these non-negotiable core values in our constitution.

If you want to protest against the current government go ahead and I'll probably support you, there are many good reasons to do that. As long as you are not supporting the movement against our country itself.