Jesus told his disciples that he will return only once and that when he does, after a time of great tribulation, it will be visible to everyone and be followed by immediate and dire consequences for those unprepared and for those who were adversaries of God.
All Christians are commissioned and obligated to be evangelizers wherever they are, in that they preach the good news to all sorts of men.
Always there have been real followers of Jesus who only worshipped his One God, the God of Israel. Many centuries they worked and preached behind closed doors, avoiding persecution and death on the balefire. In fear of the stake for centuries the real followers of God baptised people in their faith, not demanding to be part of one or another church but being part of the Body of Christ.
It is striking that there are a lot of people in the world who are opposed to those who worship Jehovah as their only true God. The vast majority of those anti-Jehovah people come from extreme right-wing groups and fundamentalist or very conservative Christian groups.
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.