You shouldn't criticize your family's religion.
Mark's family is religious and asks him if he wants to attend Church with them.
Mark wants to respond to his family's request.
Mark tells his family he respects their beliefs, but they are not his beliefs.
Mark tells his family that what they believe is not true and causes bad results for people.
Mark's family will try to be understanding towards him.
Mark's family will be offended and not want to spend time with Mark.