You are wrong about the Roman Catholic Church.
Not only do Catholics accept other Christians through ongoing ecumenical dialog, they have also reached out to other faiths, such as Jews and Muslims.
In particular there is a Catholic encyclical that enunciates this called "Nostra Aetate".
Also see [www.adl.org
"Nostra Aetate calls for Catholics and Jews to engage in friendly dialog and biblical and theological discussions to better understand each other's faith. After intense debate and some strong opposition, Nostra Aetate was approved by the world's Bishops and Cardinals in Rome on October 28, 1965. Nostra Aetate also calls for the church to dialogue with other world religions."
But thank you for firmly establishing on this thread that Christadelphians have no such ecumenical dialog with other churches and simply see the sole organized group that has the "Truth", recognizing no other church and/or denomination through ecumenical dialog.
Apparently, much like Mormons and Jehovah's Witnesses, Christadelphians teach that they alone can be relied upon as a church to attend and learn the truth and that other churches are "'lost'" and incorrect in their beliefs and practices.
I appreciate having a Christadelphian posting here to confirm this, rather relying only upon a former member's critique of the group.