Scirra must not be banning on the basis of ideological differences no matter how despicable those opposing ideals are. **** must have as much right to spout their ideology as I must have to criticise it. This is what free speech is about.
This is a common misunderstanding: free speech does not mean "you must allow people to say whatever they want". There are clear limitations on free speech. The laws vary around the world, but, for example, extreme cases like directly inciting violence are usually still banned in countries that allow free speech. So there is a clear distinction between something like someone saying they don't like a product vs. a terrorist group inciting violence - free speech still does not allow the latter. So free speech isn't an unlimited pass to do whatever you want. The UK (where Scirra is based) also has strong laws against defamation, while generally being considered a country with freedom of speech (although the balance between the two isn't always perfect).
Additionally, in the grand scheme of things we are just one small website in one corner of the Internet, and banning someone here does not take away their free speech: they can still go wherever they like elsewhere on the web or offline and continue to say whatever they like (providing it does not break the law, such as by inciting violence). I emphasise this because the "free speech means you must let me say anything I want" argument is sometimes used by people who want to be allowed to be abusive. Such people are toxic to any community and they must be removed to avoid dragging everyone down in to a swamp. I have to point this out since we've had trouble with it in the past - however out of thousands of customers, I can count on one hand the number of times we've ever even considered removing people on that basis.
In short "free speech allows terrorists to say what they want too" is actually false, and is also the kind of argument that trolls use to attempt to justify appalling behavior. Don't fall in to that trap! My main concern though is just to keep the community a friendly and welcoming place, and other than that, like I say, we're here to make games and that's what we should focus on. Our website isn't the place to come to talk about politics - we don't need those debates distracting from our actual goal of developing software - but other than that, within the bounds of the law, I don't see any reason for it to be relevant.