You can defend yourself in

People who did not restrict their AP were actually

1. trenching on public space because their signal were shooting beyond the boundary of their property;
2. broadcasting their signal, therefore they had no right to say others were stealing (can a radio stations say people who listen to their broadcast are stealing? can a resturant charge people on street when resturants' food smell going out of resturant?)

If someone break into a password protected or non-broadcasted network then and only then it can be called stealing. How can someone staying in his or her house get a uninvited signal get accused of stealing?

People who broadcast their signal should be responsible for their signal be confined ih their property even though they paid for it.