Airlines are more than capable of making decisions regarding their operations. They certainly won't be paying any attention to the rants of a spotter on an Internet forum.
I'm sure Emirates are quite aware of Prestwick's existence.
Perhaps if you're so angry about this diversion to Newcastle you should contact Emirates with your booking reference number. You don't have a booking reference? So you weren't on this flight? What concern is it to you then?
Airlines aren't charities out there to give spotters a photo op or fan boys the buzz of an extra few hundred pax through their local airport. Utterly bizarre.