Another way to phrase my opinion is pretty much this:
Wifi access points have two modes: One for the specific purpose of limiting access to people who are allowed to use it, and one for the specific purpose of announcing to the world "here's some Internet for you."
The fact that router vendors don't communicate this correctly to their customers or that they are configured wrong is, as the person sitting in the car using it across the street, not my fracking problem.
Yes, I could be charged with a crime for doing it in some states, I might have a lawyer that can't get a not guilty verdict, I might be fined, I might be jailed, or whatever. If it's the law, so be it. As to the moral question, however, I'm not having any problems sleeping at night over using an open wifi without scouting the neighborhood for a piece of paper taped on someone's door.