My grandmother is Jewish. She once tried to claim Abraham Lincoln the same way. "I was reading an article that said Abraham Lincoln had a Jewish great-grandparent" or someting like that.
I've seen atheists do this as well. They will try to claim "ownership" of people they like. I've seen this recently with both Barack Obama and Abraham Lincoln.
Abraham Lincoln wasn't Jewish or an atheist.
Barack Obama is not an atheist.
...and that's okay.
It's okay to like someone you disagree with.
Unfortunately us humans have something called ingroup/outgroup bias.
We tend to like those we see as belonging to our group, and dislike those we see as not belonging to our group.
What is often missed as that ingroup/outgroup bias goes both ways. Not only does it effect how we feel about people in and out of our groups, it also makes us want to move people in and out of our groups.
When we already like someone, we want them in our group. When we dislike someone, we want them out.
Theists are wrong about god. That doesn't make them bad, we all know that. Right?
The reason I dislike theism is because it causes harm. Most of the people it causes harm to are theists themselves. They are victims, not idiots. They have been duped.
I don't think we are going to fix that by perpetuating ingroup/outgroup bias.
So let's stop trying to claim Obama, Abraham Lincoln, and whomever else. Not because they aren't atheists, but because it doesn't matter what they believe.
At least that is one way we can get away from ingroup/outgroup bias. Do you have any other suggestions? I'd love to see them in the comments.