The First Amendment of of the US Constitution protects free speech. Though Piers Morgan is not a US citizen, that doesn't mean the same basic rights don't apply. Nor does this mean that anyone has a right to not be offended by someone exercising that right. The notion that we should deport anyone for saying anything is ridiculous and by its very nature unAmerican.
Although I personally think that Piers Morgan is an awful news caster, and a bit of a joke when it comes to replacing someone like Larry King, deportation is an awfully extreme reaction to someone being bad at their job. I think that he is an awful addition to any media he is a part of, and many times he asks horrible, inane questions.
I find Piers Morgan to be completely annoying and pompous. With that said I do think that to deport him would be unconstitutional seeing as though he hasn't done anything wrong except have bogus opinions. In the US we support freedom of speech regardless how ridiculous it might be. Our deportation system should be used for actual criminals.
I think he said it best when he said they wanted to deport him for exerting his 1st Amendment rights to talk about the 2nd Amendment. I saw the episode, and all he was doing was making the point very strongly that most other civilized countries do not allow free ownership of guns and they have very few deaths by shooting. It's a valid point. I haven't seen it written anywhere that a non-citizen cannot criticize the United States or its laws in a public discussion. Is that an attack against our county that is worthy of deportation? We would look like fools if we took this seriously.