Angora goats will eat it down completely within two years. I had a 5 acrea patch on a farm in Ohio. Ran Angora goats and within two years it was gone along with a barn yard of cockleburrs. Some Angora people were renting out goats to clear pastures.
I would suggest Multi-floral rose instead of blackberries. It gets much higher, Is stickier, harder to get thru and without goats next to impossible to kill.
Clipping one wing would help with the fly over problem temporarily. But I like the reporting for animal cruelty even better. Just about normal for a PETA. "Do as I say, not as I do".