Among the individuals who feel it's a personal thing, we observe massive disagreements with mutually exclusive beliefs.
While I disagree with "MASSIVE", you say that as if it was a bad thing.
Paul, Peter and James, didn't always agree.
Paul and Barnabas don't always agree.
Some that wrote Paul's letters for him didn't always agree with what he said.
Jesus held Peter, John and James in a special way, but Peter and John had different views about Jesus and his nature and such or at least expressed their views in different ways.
There has always been a "difference" of opinin between believers about certian things, but the core tends to be very solid:
Jesus Christ is the Son of God, our Lord and Saviour he died and was ressurected and through him we receive the gift of Grace and the Holy Spirit.