Actually a cult is defined as a group that claims to be the best,or purest form of a religion while denying one of more of that religions essential teachings.
I think its really hard to differentiate what is a cult from what is a religion. For example, the families killed in the Waco disaster were termed "cult" members. If these people had been practicing some form of Judiasm I can assure you that there would have been investigations and condemnations from every sector of government and their would have been culprits found and dealt with.
Defining something as a cult and not a religion is strictly a personal viewpoint and must incorporate personal bias.
In my experience living amonmg them, I term Islam as a political system and not a religion.
Have a nice day.