In Rome - the pagans would come to their temple to thank their god for its blessing of their lives. Then the meat used in the sacrifice of thanksgiving was sold in the butcher shop next to the pagan temple. If we wanted to buy meat in Rome the best way was to go to the temple butcher shop. Some Christians said that if you ate food used in pagan religious services it was like worshipping that false god. Others said, Oh, no.
Meat is meat.
So there was a problem. Then Paul highlights the conflict over which day is the right day to worship God. Some said, because Jesus rose on the first day of the week, they should worship on Sunday. Others said, every day is holy - so worship God whenever you want. So there was a problem.