As has been said in this thread, asking first is just good manners as opposed to the entitlement mentality. There has been many comments and threads on this forum of poor hiker behavior along the AT which tends to lower public opinion. A simple gesture like asking permission to use an outlet at a business costs nothing, will likely grant you access immediately, and improves public opinion.
Morals differ greatly in society. If one's moral philosophy is power doesn't cost much so it's ok to simply take it where an outlet is seen in a business, then thats where the moral compass points. Brings to mind an old adage, "Lay with dogs, wake up with their fleas".