Bazookas, barbed wire, lasers, killer robots... You are all out of order.
Farmstrips are used 99% of the time for walking dogs and just 1% of the time for aviation. Remember that even on foggy, rainy days the dogs are still there. To the people in the area it is the aircraft that are unwelcome guests and not the other way around.
They also don't appreciate the dangers, but this is not their fault. I am sure that if the pilots of Pprune went to a gun club the members would shake their heads at the dangerous things they'd do.
There is only one solution that works: engaging with the local community. Go out to the field yourself one day and chat with the dog owners. Tell them that they are welcome to walk their dogs there but whenever they see an aircraft approaching they should leave the field, restrain their animals until the engine is switched off and never turn their back on the air traffic.