Mark 2:15–17
“And it came to pass, that, as Jesus sat at meat in his house, many publicans and sinners sat also together with Jesus and his disciples: for there were many, and they followed him
And when the scribes and Pharisees saw him eat with publicans and sinners, they said unto his disciples, How is it that he eateth and drinketh with publicans and sinners?
When Jesus heard it, he saith unto them, They that are whole have no need of the physician, but they that are sick: I came not to call the righteous, but sinners to repentance.”
Bottom line? The guy should have just made the cake. Even if he didn’t agree with their lifestyle, it is absolutely the Christian thing to do to make the cake just as skillfully as he would any other cake.