I don't know if I was lucky or if I just waited long enough after spraying the bolt with penetrating fluid. I used two wrenches; one on the top of the filter to hold it in place and another on the bottom to loosen the bolt.

I would strongly recommend using a flare nut wrench on that fitting bolt, not just an open-end one. It'll give you a better grab, but also keep you from rounding the fitting bolt.