An aircraft receiver picking up images from the FM broadcast band would experience far greater interference from the 50kw licensed stations on the band than from 100w pirate peanut whistles.
On the other hand, a sloppily constructed pirate transmitter could easily be radiating garbage on other than the intended frequency, and that could potentially bother pilots.
I used to keep a scanner going in the van. My wife would leave her wheelchair turned on sometimes. I picked up nothing but the internals from the control box. LOL.