I would start by asking for evidence that Obama wants to take peoples guns...that seems like the simplest fallacy to tackle.

I haven’t responded yet, because It’s highly likely that if I do, the friendship will disintegrate and, aside from his political views, I do like this person.

That's your problem. I would say something like "That is the most retarded thing I've ever seen. I've lost a lot of respect for you. Shame on you."

To quote another Democratic President, "I feel your pain." More seriously, I have had the same problems. I would also do something on the order of what BishopX has suggested. I might also tell your friend flat-out that he is poisoning his own well with over-the-top comparisons that do not hold water according to the facts - that people will automatically stop listening when he invokes Godwin's Law like this - unless you REALLY think this guy will go ballistic over that. That said, do you really need to remain great friends with someone who is impervious to any reason? Or is this the sort of friendship where you don't see so much of each other that you have to be in such great accord all the time? (I forget how contacting members works around here, but if you really need to talk about this, you have my permission to contact me - like I said, I've been where you are)

Maybe I can be satisfied with not having to be always "right" in little ways when it comes to keeping a wife or girlfriend happy. But when it comes to things like this, I have to be right to keep my sanity and my sense of decency. I might remain friends with somebody who espouses this kind of nonsense, but I am damn well going to let him know how I feel about it, and if he can't take it then too damn bad. He's the one who waded into the political gutter sending this kind of crap...did he expect everyone to just "dittos" his moronic opinion?