By the passing of years it happened that some pupils came to take over teachings from other cultures and religions and as such became considered to be antichrists.
Those willing to tarnish
In the history of Christendom we see many churches which started of as so called cults or so called heretic movements, though many years later they sometimes outgrew their original group and/or became one of the many main churches. Therefore one should be very careful by damning a group or calling ti a cult or sect, when there is not really anything what qualifies it to become called a sect or cult.
Not according to legal description of a cult
Before calling a church or religious group a "cult" or "sect" one should seriously examine and clarify what one means with those qualifications.
Are the Christadelphians a Cult?
Lots of times Christadelphians are called a cult group, but they are a religious group where no specific human being is venerated and no human beings worshipped like in other religious Christian groups which are not called cults, like the Catholic Church where people pray to 'saints' and worship in front of statues.