A rabbi from a conservative congregation asks (and answers) a relatively simple question:
Just so. The Holocaust survivor is wrong, obviously so – but you can understand why he’s wrong and you can hardly be surprised at his feelings. And while you might strenuously disagree with his opinion, you would still embrace him with love and welcome him into your community and maybe even into your house from time to time. And you would resist the calls of other people that you act ashamed for having done so, despite the obvious wrongness, and indeed offensiveness, of the anti-German prejudice your friend evidenced.
The analogy isn’t perfect, of course. But it’s close enough to understand where Obama is coming from.