Most likely, swastika cakes are not a service that any bakeries (Jewish or otherwise) offer to anybody. The issue here is a minority getting the same service already offered to everybody else. Are you being this obtuse on purpose?
Some bakeries will put whatever you want on a cake, no questions asked. Why shouldn't gays or Jewish bakers be held to the same standards? The issue is forcing someone to do something they find offensive, ratifying, under penalty of law, something they don't believe in.
And when a gay bakery, who writes messages on cakes, (rightfully) refuses to put a pro-tradtional marriage message on a cake, why isn't that issue a minority - religious people who think gay marriage is a sin - getting the same service already offered to everybody else, too? Are some minority groups more special than others?
Find me a bakery who will make a swastika cake. I triple dog dare you. There's not one. It'd be all over the news and they'd be out of business immediately. You are so full of shenanigans on this one! And as for comparing gays to Nazis, there aren't enough emoticons in the world for that.
And why not? If I were a baker, I'd bake someone a cake with swastikas on it if they wanted one. I'd bake someone a cake with a Confederate flag on it. I find those things offensive, but running a business is not the same as acting in a personal capacity.
This is where I tend to disagree with both the cultural Left and Right. A for-profit business serves no purpose other than the maximize the financial returns of its owners. It serves no social purpose. It serves no cultural purpose. When you deviate from maximizing profits, you get into issues like this.
Some liberals try to square the circle by promoting "social responsibility" and "environmental responsibility." If pursuit of profit creates negative social externalities, the answer is to tax the businesses and regulate them in such a way that they bear the cost of those externalities. It's not to try to change the very nature of what a for-profit business is.
Some conservatives have taken corporate personhood to a new extreme and decided businesses can have morality and values. They don't and they shouldn't. There is no such thing as a Christian business or a Jewish business or a Buddhist business.