@Anon-e-Moose:
WARNING: VERY LONG.
Actually, we do have a 'Constitution'. It's just "unwritten", which is to say that the laws protecting our rights are all over the place in the law books, rather than codified into a single document called a Constitution.
And as for arrest for protesting against the practice of homosexuality: while it might be morally wrong, if it's peaceful and polite, it isn't doing any harm, even if it is offensive.
The police and the law feel the same way - it is actually legal to do this, and it should be, because if you start "thought policing" (Woo-oo! Fundy boogeyman! >:D) on that subject it does encourage the policing of other subjects*. The law makes no legislation barring expression based only on (read: there have to be other factors involved) the fact someone finds it offensive.
The reason Fred Phelps and his little brood of vipers wouldn't (and shouldn't) be allowed to preach their brand of hate here is because they deliberately do it to cause upset. Not 'upset', meaning 'a little hurt because someone took the piss out of my opinion', please understand, but genuine upset, meaning 'causing emotional distress, causing anguish, reducing someone to tears'. The fact that it's offensive doesn't enter into it: it's emotional abuse, which is far worse, and that's why it's not allowed.
Those could be considered the "other factors".
For any Americans reading this, it would be the same as those bastards from Anjem Choudary's mob that started slagging off British war veterans during the Memorial Day service last year. That's why it's wrong: because it's harrassment and bullying, not because it's offensive to some people, or even all. And if the U.S. legal system can't see the difference between that, and assume that the 1st Amendment trumps all, even when the distinction is made in U.S. law, then I'm sure you'd agree it's in a lot of trouble.
Look up Gary McAlpine for further reading: he preached that homosexuality was wrong in a polite manner, and they didn't prosecute him.
They checked with the Crown Prosecution Service to see if a case could be make, and were told that of course there wasn't, so no prosecution.
Also, I found a video on Youtube somewhere recording the arrest of another preacher in the same manner (it could have been Mr. McAlpine, for all I know), and they were just asking him to come down the station to ask him what he was up to. They explained themselves and said that there's a bit of a grey area and they believed that what he was saying fell into that, so they wanted to clear things up.
So legal or not, I can hardly blame the police for taking them down the station for questioning, as even when you preach something like that politely it's a bit of a grey area!
Funny how this ties in with what I was saying in my previous post, eh?
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*Remember, the only disagreement that fundies have with "thought police" is that they aren't on their side; they're more than willing to use "political correctness" themselves to silence dissenting opinions because they find them offensive.