Clanad...with the greatest of respect, I must disagree with you.
First of all, your analogy of the no shirt sign, no service is entirely disingenuous...it has nothing whatsoever to do with discrimination as discussed in this thread.
Homosexuality, your race and colour are accidents of birth, over which nobody has any choice. But religion is a choice that people can make. All over the world people are fighting and dying for issues such as religion, but I have never heard of Christian and Gays murdering each other over issues such as cakes !
You bring up the American Constitution. You are on rocky ground for a start there. If we could go back in time and ask the founding fathers whether the bit about bearing arms was really meant to ensure that 1000's of innocent people were to die each year, especially many entirely innocent children, mowed down while at school, I am 100% convinced that they would say no, of course not and be horrified at our stories from hundreds of years later.
But I don't like to intrude upon personal grief and you and your countrymen will have to fight that one out for yourselves. I for one, am glad that after 2 serious massacres, gun ownership is severely curtailed in Britain.
The bakers in this case choose to be Christians and go further by choosing how their interpret their beliefs. But the people who tried to order the cake didn't choose to be gay. The choice of that was denied them by nature.
I am not sure if you are an American or a Brit living in America but we have many laws, keenly fought for, to protect the innocent from being discriminated against. I am unsure if you have similar enlightened laws on your side of the Atlantic or not. If you don't, then the bully and the bigot will continue to prevail.