First of all he says that if someone invites you to dinner they were to ask no question for conscience sake. If we don't know where it came from we are free to eat it. Next though if he says it came from an idol's temple then it is a different story. Then they were not to eat because of the conscience of the other person who invited him.
Now this could be played out in our modern life too. Some may be free to do things that others would cringe about. We are to be gracious about this
as Paul seeking the other persons well being.