Just imagine the scanner outputs a stray signal on the
navagation receiver or it blocks a transmissoin from the tower at a critical
point.

I know some people who live right near airports. (almost right next to the
airports).

could them listening to scanners in their own homes interfere with the
airports' and airplanes' navigation sysyems and cause the planes to crash?

I hope not, but it sounds to me like they can from the information given in
this newsgroup.