Paul was writing to a church that was made up of people from very different backgrounds, as had he been when writing to the Corinthians.
"Some of you are strong enough in your faith that the rules the others hold to seem petty to you." Once Paul had criticized Peter for siding with those who insisted on following rules. Now, Paul seems to be siding with them himself.
"If you love them, treat their needs seriously. After all, we are in this together. After all, we owe our allegiance to God."
(I've been reading Garry Wills' What Paul Meant.)