"You can support Islamic Radicalism in America. You can even claim to be part of Radical organizations."

Well, not entirely. The Antiterrorism and Effective Death Penalty Act of 1996 makes it a criminal offense to provide funds or other forms of material support or resources, such as weapons, safehouses or printed materials supporting the cause, to designated foreign terrorist organizations. The law applies to anyone within the United States or subject to the jurisdiction of the United States, and violators are subject to fines and up to 10 years in prison. You don't have to enact violence at all. [1]

"Any display of Nazism in Germany is persecuted. That's wrong."

You're right. Basic Law for the Federal Republic of Germany made it illegal to have a political organisation that did not adhere to the democratic foundations of the German state. This constitution was co-drafted and co-signed by the United States along with all the other allies involved in the war. [2] Any political model based on the principle of Führerprinzip was banned, as it was identified during the Nuremberg Trials as one of the key defences of Nazis on trial. You can't come froma country involved in the drafting of a constitution that bans Nazi political parties and then attempt to use that ban as a comparison of why your country is better with free speech when they actually follow through with the ban.

"Sharia Law creates exceptions for Muslims. That they can defy the court system and go under their own court system."

That would be true if it were the case, but unfortunately it's not. They're not courts; they are arbitration tribunerals [3]. Anyone can choose to settle a dispute (as long as police charges have not been pressed) via an arbritration court, which is essentially a voluntary and legally binding contract set up between the two parties for situations that fall outside of UK law, or for which the CPS have chosen not to press charges. Their only legal power is that they are legally binding contracts which have to comply with UK law; they are not legal rulings and never will be. [4] If two muslims wish to settle a dispute that falls outside of the bounds of UK law with a written contract which happens to be based on Sharia Law (which they have both agreed), why would you want to stop them? Do you think government should be involved in stopping contracts that two citizens draw up between themselves? There have been Jewish arbitration tribunerals for ages, and no one kicked up a stink about them because they aren't given the same stereotypical perception that muslims are.

"Even UK liberals are against this (at least, the Atheist kind)."

Please don't presume to think that you know about compex issues occuring within the UK. I know plenty of liberals (the VERY athiest kind) who, rather than becoming all hysterical about a situation that they don't quite understand, took the time to look into it and make an informed decision about the situation. The UK media, especially the tabloid media, have whipped up a frenzy about nothing. I don't particularly like the idea of it myself, but that is based entirely on my religious biased and not on the facts of the matter.

I'll even go out on a limb and say that, in general, the US probably has one of the best models in the world for the protection of free speech. What I can't stand though is hysterical nonsense where people don't actually understand the situation at hand.