Metro Etiquette

You're on the subway and it's really crowded. You take the only seat available -- next to a stranger -- who for the sake of argument is an overweight minority. You are comfortable enough in the seat, though the size of the stranger means you two are more snug than usual.

Eventually you get near the end of the line and the train car clears out. There is an empty bench right across the way. You're sitting on the outside, so it would be easy to slide over. Do you move?

Everybody enjoys some personal space and, let's face it, you'd both have way more if you moved to the empty row. But will the move be construed as disgust or bigotry.

What is the proper thing to do in this situation?

My first instinct is to stay in the chair. That way no one's feelings get hurt, even if it makes for an awkward situation. But is that just being over-sensitive?

Here's an urban etiquette primer, but I didn't find what I was looking for there.