So some guy who just happens to have the names Adolf and Hitler (both of which I believe used to be very common, actually) decides to perform genocide, and suddenly people aren't allowed to name their kids either of those? Idiotic. "We make custom cakes for people, but if you have a name we don't like we're not going to do it, 'cause we're jerks like that." That's the impression this incident gave me; that we're just going to fall to name-based discrimination in the absence of other forms of allowed discrimination. Ignore for a moment the fact that one of the many people who have had those names (many of which probably weren't racist) decided to do something crazy, and think about the name itself. It could actually sound like quite a nice name to some people. And so what if they are neo-nazis? That doesn't mean that the cake should be denied. "Normally, we'd make a cake with the name Adolf on it, but since you follow this political belief, we're gonna say screw you." This gives me the impression that they are willing to act on political discrimination.
Political freedom is an American right. In case you haven't noticed, being a neo-nazi or communist isn't enough to be jailed. If it were, that would be one step closer towards being able to discriminate against democrats, or republicans.
And it should go without saying that you have the right to have your name printed onto something that you are paying for.
Honestly, you can find Mein Kampf at a bookstore, and that's far more iconic of the terrors of nazism (seeing as how it actually spells them out) than a name. A child should be able to have his name on a cake.