No, it is stealing. Nobody is listening to background noise. And if a pirate is running their station like a commercial outlet, selling ads, it is stealing ad dollars and underwriting dollars away from real radio stations. They pay all the necessary fees to do what they do.
I had a friend fix my car with a car part I bought online. I paid my friend cash. He's not going to report that cash on his taxes as income. I suppose I vaguely interrupted the revenue stream to my regular mechanic. Is this "harmful" ?
No, because he's not breaking the LAW by fixing your car. There's no license needed to fix your car, and your car isn't a limited resource that needs a band-plan and licensing to keep it from turning into CB. And by the way, you DO need a driver's license, don't you. What happens if you drive without it and get caught? Why not do away with drivers licenses because the under-served can't make it to the DMV? C'mon, let's use a little bit of logic here. This isn't some kid goofing around for a couple hours on an empty frequency.
If they were that serious about radio, buy a damn station. The prices are right these days. And if it's an AM legally, not an FM illegally, then that's the way the ball bounces. Raise more money with the AM and buy an FM. I'm sick of this "Occupy Whatever" mentality where it's okay to take things because you think it is okay and "deserve" it. No, I shouldn't pay for some kids college, and I shouldn't have to try and run my business with these knuckleheads taking away revenue from real stations that pay me in real money.