So Merriam Webster is irrational? Or maybe you're just a little hyperbolic?
** a religion or sect considered to be false, unorthodox, or extremist, with members often living outside of conventional society under the direction of a charismatic leader.
(also interesting in the definiteion of "cult"...
** any system for treating human sickness that originated by a person usually claiming to have sole insight into the nature of disease, and that employs methods regarded as unorthodox or unscientific.)
Shall I list a few of the religions that have been classified as cults using this definition, down through the centuries? As can be seen by legal and mob persecution against them.
Christians, Jews, Mormons, Catholics (in Russia and elsewhere), Orthodox Christians (in Poland and elsewhere), Hugenots, Waldenses, Jehovah's Witnesses, Hasidim, Unitarians, Anabaptists, Seventh-Day Adventists, Mennonites, Christian Scientists, Quakers.
That's just off the top of my head.
BTW, I don't object to Boortz believeing Islam is a cult. I object to his stating his personal opinion as a fact. "Islam isn't a religion, it's a cult."