My friend said that his church also teaches that you HAVE to participate in the Lord's Supper too. Which I do believe it is an ordinance. But they believe that it HAS to take place on Sunday of every week.
Also they believe that they can fall away from faith and that they are the only church that worships correctly. As my friend once said that it is better to do things correctly than with sincerity.
From my limited undersatdning of the history, Barton Stone desire that there would be unity among Christians. His intent was that creeds would not damage the relationships between believers. He spoke later in his life that he was concerned about the extreme measure that the movement has taken on since it became exclusive.
How do we find a common point of discussion in striving for unity when they believe they are the only true church?
There is a joke:
A person died and went to heaven. When he got there, he was being shown around the place when he and his guide passed by a high walled enclosure.
The person asked about it and was told "Shh...that's where the church of Christ people are...they think they're the only ones there."
You will have trouble convincing someone on doctrinal grounds who is happy with their church about the right or wrong of their doctrine (and this is true about anyone who is happy in their church.)
You have a couple of choices:
Churches of Christ (outside of the ICC) aren't a mind control cult, just conservative, although a lot of them believe the exclusive bit. They believe that Jesus is the Savior. They treat baptism and the Lord's Supper like sacraments, not ordinances, but don't call them that...they are baptised in the name of the Father, Son and Holy Spirit, and take bible study serious. They, for the most part, believe in the Trinity.
Because of this, you can agree to disagree and just chalk them up for being kookie, but Christian.
or you can wait until they are unhappy and searching. Show them how to be better fed somewhere else and they may go.
For me it was church history that started me disagreeing with the Restoration concept. And that led me out.
Through love.
Look - over the years and in discussions with Christians as they state why they believe what they believe, this is what has been remembered - "they are the only true church, they believe you have to be baptised, they do not believe in instrumental music".
If you base the tenets of your church on the Bible's instructions for the Church - of course, you will believe that is the true church. Why not?
Should man look to other men to see what is to believed or should man look to God and His Bible to see what God wants?
I feel it is far wiser and safe to look to God - not man. We are told do not add to or take from the Bible.
Now, how many men love to add to or take from the Bible in order to set up the creeds they like and develop them into a full blown church? Are you willing to base your salvation on what a man tells you is right - even though it is not found in the Bible?
All the Church of Christ is doing is going to the Bible to set up their churches. When they are asked why they do not have instrumental music (a small matter IMPO), they, of course, say "because we were not specifically told to do so in the Bible". Now why is this so weird? I can find much more weirdness just by looking at TV everyday.
We do not say all who are not Church of Christ are not saved - if they follow the instructions for salvation they find in the Bible. All they have to do is believe in Jesus and accept Him as their Savior, repent of their sins and be baptised for the remission of those sins. It is very simple and is merely what God told us to do in order to be saved.
We cannot tell any they are saved by other means because we have no authority to base that decision on. How would we be able to determine what God will accept as the way to get salvation unless God, Himself, told us. That is what He has done with the Bible - told us.
It is up to God to decide if He will accept other ways of getting salvation - not members of the Church of Christ or any church for that matter. We only state what the Bible says to do - we know that works.