We recently wondered why members of the Dor De’ah movement, on the one hand, and Satmar/Munkatch on the other, are treated so differently. The former are vocal unbelievers in the Zohar, who accuse generations of Jews of being quasi-idolaters for believing in a pleroma, the latter similarly regarding anyone not sharing their Satanism as denying the Final Redemption (and so on). Both freely refer or referred (Dor De’ah is past its heyday) to millions of Jews as heretics, but only the Darda’im were seriously treated as sectarians.
I gave my own answer above. Here is Rabbi Grossman’s answer:
In my experience, the major difference is that the approach of the Darda’im (and the Rambam, BTW) is inherently subversive and therefore a perceived threat to the rabbinic establishment. As you have read in my recent article, Rambam could dismiss an established custom, endorsed by centuries of practice and by the Geonim, if he was convinced of its heretical source. I will dub this “Rambam’s Razor,” and in recent discussions with older scholars, I could clearly perceive their subconscious realization that such a methodology could radically change halachic practice. Of course, from an objective standpoint, the truth is the truth, and we should not take matters of Issur and Hetter personally, as though we have a vested interest in maintaining certain opinions in practice, but for many, they are just too uncomfortable with it.
The Darda’im, as the Rambamists par excellence, represent undermining tradition, even if we know they are really just trying to restore older traditions. Anti-Zionists, however, have appearances totally on their side, and from any point of view but the most perceptive, represent the strictest adherence to tradition in practice, and their opposition to Zionism is tolerated because of Zionism’s perceived novelty and therefore suspicion.
May God grant us the ability to properly analyze and fully understand each approach and its consequences.