Have totalitarian authority and make liberal use of the guillotine. Throwing out everyone you don't agree with will give you a party of one. You are endanger of becoming what you oppose.
The following is a good definition o fanaticism from a paper:
An excerpt from: Modern Judaism and the Haredim – Charles D. Isbell, on
“Fanaticism” might be used alongside of “Fundamentalism” as a proper description of the haredi groups as well. In the apt description of Paul Tillich, a prospective member for such a group may be seeking to escape, “from his freedom of asking and answering for himself to a situation in which no further questions can be asked and the answers to previous questions are imposed on him authoritatively.”7 That is why members of such
73 groups often appear to be so harsh and unbending to anyone outside their group, yet understand each other perfectly well. They have all accepted the same absolute authority. But there is another product of such groups. Here is Tillich again:
Fanaticism is the correlate to spiritual self-surrender: it shows the anxiety which it was supposed to conquer, by attacking with disproportionate violence those who disagree and who demonstrate by their disagreement elements in the spiritual life of the fanatic which he must suppress in himself. Because he must suppress them in himself he must suppress them in others. His anxiety forces him to persecute dissenters.8
Now Tillich was not describing any particular fanatical group, but fanaticism in general. But we will see that this general description may be applied appropriately to haredi Jewish fanatics in the twentieth-century as well as to some of their classical predecessors. We must also remember that Tillich, a Christian theologian, knew about fanaticism from first hand experience in his native Germany, where he was the first non-Jewish Professor to be dismissed from a German university because of his vehement opposition to nazism.
http://www.umass.edu/judaic/anniversaryvolume/articles/06-A4-Isbell.pdf