Paul’s point in Romans Chapter 14 is that even as Christians being led by the Holy Spirit we are not going to agree on everything. We may have differences of opinion on doctrine or personal preferences and that’s OK. How do we then function as Christian brothers & sisters?
In vs 2-6 he’s talking about eating or not eating meat, or observing certain holidays. We can have differences of opinion but he says we can’t fall out of fellowship with each other over these types of non-essential issues.
Paul had just stated in Chapter 13 that love was to be our guiding principle. Here he’s saying we can disagree and still be loving but we can’t do it in a judgmental way. We can’t look down on others and we can’t condemn others who think differently than we do. We have to operate with love.
Paul says we have to live in a way that doesn’t cause other believers to stumble. That means we can express our opinions, we can share ideas, and even try to encourage someone to change their thinking on an issue. But we must do it in a respectful, caring, loving way not a judgmental and condemning way.