This happens with sickening regularity with bakeries, inns, restaurants, and other businesses. For those Christian owners of businesses who would consider doing this to a client, let me tell you in no uncertain terms that this is not what Jesus would do.
Jesus was very clear on how we are to behave toward everyone. We are to love our fellow Christians. We are to love our neighbours (and that includes everyone-- not just those of our faith or nation). We are to love our enemies. In fact, we are to go above and beyond for our enemies and those who force us to do things we do not want! We are told to give more than is demanded, to go the extra mile. (Didn't know that was from the Bible? Look it up.) While most of us would hesitate to label someone with whom we disagree on some religious matter an enemy, this still sets a model of Christian love, compassion, and humility.
We are called to do for others as we would want done for us. If you were to go into a bakery run by someone who had been hurt by Christians so much that he or she believed that Christianity was immoral, and if you asked for a cake to celebrate your child's baptism or first communion or confirmation, would you want to be told that the baker didn't bake cakes for Christian events because he or she didn't agree with our beliefs or lifestyle? How would you feel?
Would it be right for a bed and breakfast to refuse to honor the reservation of a honeymooning interracial couple because they sincerely believed the Bible says that mixing races is a sin?
Many Middle Eastern Christians shop in grocery stores run by Muslims because it is the cuisine they know how to prepare. Should the Muslim store owner refuse to sell to Christians because he does not agree with their beliefs?
Our Christian witness is so very badly damaged when we act loving only to those who share our beliefs and discriminate against those who don't. We are seen as hateful and prideful and hypocritical in ignoring certain sins and only refusing service based on others to which we are not subject.
Jesus said, "I was hungry and you gave me something to eat. I was thirsty and you gave me something to drink. I was a stranger and you invited me in. I needed clothes and you clothed me. I was sick and you looked after me. I was in prison and you came to visit me." In Romans, Paul instructs us, "Bless those who persecute you; bless and do not curse. Rejoice with those who rejoice; mourn with those who mourn. Live in harmony with one another. Do not be proud, but be willing to associate with people of low position. Do not be conceited. Do not repay anyone evil for evil. Be careful to do what is right in the eyes of everyone. If it is possible, as far as it depends on you, live at peace with everyone."
Our efforts on behalf of people with whom we disagree should be exemplary, our absolute best.
Let it be said of us all, on the judgement day, "I needed a wedding cake, and you baked the very best one you could. I needed a place to stay, and you welcomed me so warmly. I needed a pleasant meal and time spent with my beloved, and you made sure my evening was perfect."