Good article. I especially appreciated the observation that like literally ALL cults, the Christadelphians teach the same two lies: 1) That Jesus, as a created being, was not divine (and also not pre-existent) and, as such, needed salvation from sin. 2) That adherents must work for their salvation.
The article cites all the Scripture references that puts the lie to the Christadelphians doctrine (and that of all other cults which teach the denial of Jesus' divinity and the promotion of works-based salvation).
That's why I think it is a bit of an overreach to say that the RCC teaches works-based salvation and is a cult-- (although there may be elements within the Vatican which are a cult--maybe even a Satanic cult, if some of the accusations are true). Standard RC doctrine names Jesus as the divine Son of God and their standard doctrine also teaches that no amount of good works can save you--that you could give all of your money to the poor, live an exemplary life, and still go to hell, if you have un-repented sin. I have a bit of a problem with the last part because somehow it always ends up with the priest having to say magic words over you so you don't go to hell. But, I probably have more in common with an RC who adheres to standard RC doctrine than liberal "Christians" or those in "Christian" cults.
But their standard doctrine is what defines Roman Catholicism.
So that doctrine is cult, it's followers are cult.
Degrees of cultism is still cultism.