Often a lot of people do not know to differentiate between Christendom, Christianity, religiosity and even limit religiousness to Christians, forgetting that there are many other religious groups who have all sorts of worship.
People should know that false teachers will teach anything they believe, and not from the Bible. People also should look at the preachers their behaviour and see if they have the Holy Spirit in them, following, living according and teaching the words of the Holy Bible. Often their way of talking, using a language which is not according the way Jesus would talk shall dismantle them and should be a sign for you that they are not the right one to follow.
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.
There are no proven external defects in the witnesses all those Biblical authors and contradictory to the adversaries their sayings and writings, no internal defects in their testimony can be found either.