I didn’t find the amnesty quotes at the link, but when running with McCain, Palin expressed support for all his policies, which was completely appropriate.
As I recall McCain’s plan, it involved people returning to Mexico (or wherever) and waiting a period of years for a legal reentry. Correct me if I’m wrong. In any event, people would not even go near it because they are so opposed to amnesty.
No, it's not appropriate. Saying, "John supports this, but this is our difference in opinion" would have been appropriate. But lying is never appropriate. I don't believe Sarah to be a liar, I just believe her to be wrong on this issue which is a very important issue.