“Now as for a person whose faith is weak, welcome him-—but not to get into arguments over opinions. One person has the faith that will allow him to eat anything, while another whose faith is weak eats only vegetables.” Romans 14:1,2
It’s the same basic advice that Paul gives when talking about meat being offered to idols.
What Paul means, as I understand it, is that he’s talking about how to deal with contentious issues in a peaceful manner.
As hard as Christians will study the Word of God, they are not going to always come to an agreement, so it becomes a question of how people can get along with each other, despite their disagreement.
What Paul advises is that if you believe something is wrong to do, don’t do it. Have a clean conscience, but don’t harass somebody to not do something they think they are free to do.
If a person believes they are free to do something, go do it. However, if you come across somebody who does not feel free to do something, don’t harass him into abandoning his position.
Unless it’s a gross wrong, Paul is, more or less, advising people to live and let live.