My first worry is not a huge issue in the scheme of things, but let's look at this paragraph:
Further, the chances of Mr Assange receiving a fair trial in the United States appear remote. A number of prominent political figures have called for him to be assassinated, and the Vice-President has called him a "high-tech terrorist". Given the atmosphere of hostility in relation to Mr Assange, we hold serious concerns about his safety once in US custody. We note that Mr Assange is an Australian citizen, whose journalistic activities were undertaken entirely outside of US territory.I agree with it all except the bolded sentence. I'm not in a position to say that the odds of the trial itself being conducted fairly are, or even "appear", remote. I don't think that's the point.
The last sentence is one I strongly agree with, though it is a bit obscure just what it's getting at. The real problem here is America's peculiar propensity for extraterritorial criminal legislation. The actual trial might be conducted fairly, but people who are not US citizens should not be tried under US law for activities outside of the US. If Assange did something that was illegal in whatever country he was in at the time, it should be up to the authorities of that country to decide whether it wants to prosecute. American law should have nothing to do with it, and no country should ever agree to the extradition of a person who is not a US citizen to face charges for conduct entirely outside the US. Although I wouldn't put it this way in such a letter, America's arrogance in this regard is appalling.
My second worry is just this: surely something could have been said to help distance the signatories from the widely-expressed view that the pending charges against Assange are absurd and trumped up, and that the women concerned are somehow disreputable or of no account. I realise that it wasn't strictly necessary to go into the issue, but I'm uncomfortable that nothing at all was said to make clear that the letter is neutral on the merits of Assange's conduct in Sweden.
I'm open to argument on this. I do realise that there's a risk in opening a can of worms here, and I'm not sure what additional wording, or tweaking of the current wording, I'd have wanted. Perhaps I'd have signed up if asked, after due reflection, but I'm not in a hurry to bounce up in the comments on the site saying, "Me, too!"
As to Assange's bedroom conduct, perhaps we'll find out more about what really happened if the case ever goes to trial ... or we'll understand more clearly. We can then make up our individual minds about how morally vicious or otherwise it was; whether it was the sort of thing that should have been criminalised; if so, to what degree; and so on. I have no opinion to express on any of that at the moment.