Do Christians have to agree on everything? I sure hope not! There are all sorts of issues about which good, well-meaning Christians hold different opinions. Some that I have come across in ministry: Which is the proper day to consider the Sabbath, the morality of drinking alcohol, the best version/translation of the Bible, the correct mode of baptism, the "right" political party, recommended attire for worship, suitable activities for youth groups, the standard of the tithe, and the appropriateness of Santa Claus!
It's enough to drive you to distraction! And that's the problem. Should we argue (usually endlessly) about such things?
Paul seems to conclude in Romans 14 to simply let "disputable matters" alone. He cites the contentious examples of observing special days and eating meat, probably holdovers from pagan traditions. Paul basically says that things like these are matters of opinion not worth fighting about. If you believe something debatable is sinful, then for you it is sin. But if your conscience in the Holy Spirit is clear about something, than for you it is not sinful. Yet, Paul states, don't use your freedom to wound the conscience of another believer or drag them into sin by your actions.
It seems that the Church would be much healthier if we could agree to seek unity on matters of central importance, and adopt a "live and let live" attitude where it pertains to opinions on side issues. Of course, the catch is often determining which modern questions are central to the gospel and which are merely peripheral! It would be nice to have Paul weigh in on that!