I consider it a sin when someone rejects the Teachings of Christ or His Church, "the pillar and foundation of truth." Catholics call such a person a formal, or in your case, material heretic.
So what does the Bible instruct us to do in such a case?
I know, we should take our dispute to "the body of believers." Well, who would they be?
There are countless Protestant sects with important doctrinal differences. How can they possible resolve any doctrinal dispute?
And if Christ's Church is invisible, then His instructions would be moot, void, or nonsensical, which is an impossibility for Christ.
Well; ain't that special!
I consider it a sin when some 'church' adds a bunch of stuff that is UNPROVABLE and extraneous to it's rituals.
So countless that the 'differences' cannot be named?
Give us some specific examples please.
That kind of charge is constantly being thrown out there but rarely, if ever, are specific examples forthcoming.