I'll try to be quick.
When you have political parties that are not committed to democratic rules and to truth, and so on, in a political system there are no easy answers. They pose a series of dilemmas. Do you crack down on them? Do you treat them as illegitimate, but then run the risk of reinforcing their appeal? Or do you ignore them and run the risk that they gain in popularity? There are really no good answers. I think there's a series of bad options and worse options.
One of the critical points that, I think, merge out of historical records is that one does need to act with forbearance. In other words, one does need to act with self-restraint. One does need to try to treat these other parties as legitimate representatives of the people who have voted for them.
On the other hand, one has to beat them electorally. I think that at the end of the day, the point of a democracy is that you can win in elections, and this sends a message to parties that what they're offering doesn't work.
It's critical to not limit their access to institutions, on the one hand, but on the other hand, one has to draw a hard line and not form coalitions, for instance, with them.