Romans 14

Now, don't go around all puffed up because you have faith and another's faith is week.  This is a "love your neighbor thing." Go out of your way to honor your weaker-faithed neighbor. Here Paul is talking about people on diet or activity restrictions due to religious reasons. Some customs, while unnecessary, are not harmful and really are not important for us to correct or, worse, judge ourselves better than another. Let God sort it out. Remove stumbling blocks from your neighbors. Don't create them. Build up (edify) others. Faith is about acting out your devotion to Christ and not about fussiness in correcting others.