"Many of these groups"?
I am speaking of the divided wings of Catholicism: Roman and Orthodox.
What are the basics of the message: "Love your neighbor as you love yourself, and love God above all." Jesus said that these two Commandments were the ENTIRETY of The Law and the Prophets. In other words, on God's authority you may now fold shut your Old Testament and read those two commandments over and over again, because God has told you EXACTLY what GOD inspired in the Old Testament. The rest is detail, and it can confuse people. It can actually lead people AWAY from God's Two Commandments, if they read into the Old Testament MORE than the Two Commandments that God Incarnate said were the ENTIRETY of the Old Testament.
Any disagreement on that?
If there is, then you've gone off the message of Jesus.
Says who?
HIM!
So, that's the whole Law and Prophets, the whole OT, according to God: "Love your neighbor as yourself, and love God above all." He gave some specifics about HOW to love your neighbor as yourself: practice charity, tell the truth, do not gossip, be meek and avoid violence.
Got it.
Now, what else did God say in the New?
Well, he gave us a Church, and he left it under leaders with the power "to loose and to bind". And THEY told us to lay on hands to impart the Holy Spirit (Confirmation) and how to select the clergy and lay hands on them (Ordination).
Jesus told us to baptize, and did it himself (Baptism).
Jesus healed the sick through prayer and told his followers to do so (Anointing of the sick)
Jesus and his apostles called for the repentance of sin (Penance).
Jesus performed his first miracle at a wedding in Cana, and he told us marriage is holy and made by God (Marriage), and not to break what God has made.
And finally, Jesus told us to break the bread and take the cup in memory of him (the Eucharist).
Got it.
Seven sacraments and two commandments.
That's it.
That's the message.
There isn't anything more to it than that.
The rest is detail, and the details are not sufficient to keep us separate.
Oh, and he also specifically said, when his apostles were trying to stop others preaching and casting out demons in his name, not to stop them, because "Those who are not against us are with us."
Nothing about this is hard to understand, although much of it is quite hard to actually DO. Especially the part about being nice to others.
What do YOU think are the vital parts of Jesus' message that force us to reject each other and not walk together all the way to St. Peter's gate?
I was speaking more generally of what calls itself Christianity at large as opposed to what actually is.
One Quibble as a matter of reverence - It's God's gate, not St. Peter's. I know you'll see that as a matter of point of view from experience. Semantically, you may see it as no difference. From a point of due dilligence and reverence, to me it is an all important distinction.
When God acts through a man, the action does not belong to the man. Man may assent to God's leading, but the only thing the man owns is his assent - everything thereafter belongs to God. And this is why we're to give God the glory for all things. That being said, I don't see any part of the scriptures as less important than another. We are not to quibble over tie vs. no tie issues; but, that isn't legislated by scripture. Congregations decide those things for themselves within the limits of what scripture says is proper - hopefully.
There is no detail in scripture that is not there for a purpose. To suppose we can extricate parts we like, agree on them, and toss the rest aside as debateable is to say, "part of this is true, the other part.. maybe". God didn't say 'here it is, take what you think you can all agree on.' He rather said, here it is, take it or leave it. God authored the covenant, not us. God sealed it, not us. We have the right of free will in accepting or rejecting it. But nowhere, nowhere in scripture will you find the right given to man to change the covenant.
I know you'll say it isn't "changing" the covenant when agreeing just to the parts to it that are unoffensive. I will argue that it is because you're picking and chosing what the covenant will be for yourselves. And that goes for all parties at the table. If you prefer your version of Sin definitions over that of scripture, you have a different system than the covenant defines - that means your covenant is different than anyone who takes the scriptural tack. Just an example.
It is simple - very simple and clear when broken down to it's basics. I've signed contracts before. When you sign a contract, something in that contract vs. something not in that contract is a world of difference. If you and I take the same contract for marriage and you add a prenup to yours while I don't, we don't have the same contract. We may have assented to marriage; but, our covenants are different - you have different rights. That isn't the way God's covenant works. All of us are bound by the same contract. And we are not allowed to change it. We didn't set the conditions, God did. And when you start talking about "what in the message we can agree to" you're essentially redacting the parts of the covenant you won't agree to whether you'll admit it or not. Then you'll debate the rest later and maybe accept a little more of the contract or change it further with your own ideas.
When you begin redacting or adding things to the scriptures, you're telling God and all of us that you have usurped the authority of God and are changing the covenant. That is a usurpation not unlike that of Satan. "I will.." Satan wasn't content with what God willed, Satan's will got in the way and he decided he'd rewrite the order of things in heaven. Very simple to understand; but, it doesn't seem to ocurr to people when they start doing the same thing themselves that the same result follows - being booted out of eden.
Assent must be assent to the whole message, not the bits we like. And it must be restricted to the message, not the message plus philosophies we include without authority to so do. Assent must be to God's covenant with us - not our rewrite with submission to god demanding signature for same. And I'm not unaware that there are councils among some groups that meet and act as signatory for God when he doesn't give his own assent to our will.
I don't pretend these are not harsh words for the ears of many. They are stated with as little specificity as possible in order to note that all are guilty of these things - all. If we have the wisdom to correct our own stances and adhere to the actual covenant rather than what we try to change it in to - to that extent, we are spiritually already brothers. To the extent that we give assent to others altering the covenant, we've already blasphemed God in our assent to such.