Are they owned by a Famly? If so they can run it anyway they wish! otherwise, there freedom is being infringed upon.. What about yours, well you have a right to read it or not right?
Its their truck. If they want to put religious stuff on its their $$. If it bothers you go someplace else. I worked for BoWevil Express a few years back. The guy that owned it was real religious and all their trailers had scripture on the doors. They even had a company chaplain on the payroll and that was his only job. They didn't force it on you, they treated the drivers pretty good, and the paychecks were on time.