Install OC canisters next to the headlights (but tucked away under the hood) that can be activated from the driver's seat.
But an extra car battery and and transformer. Turn your hood and fenders into an electric fence.
Put a REALLY LOUD speaker in your grill and blast Disney Princess music. If that doesn't pacify them, switch to something a little more offensive, like Toby Keith's "Courtesy of Red White and Blue".

EDIT: After some deep contemplation and self-reflection, I realized the answer was right in front of me the whole time: Play the National Anthem and they will stop everything just to kneel down.
Use a modified windshield wiper fluid system to spray elk piss (or something equally pungent) in a wide spray pattern all around your car. Make sure your external air vents are closed.
Keep a feral hog in your trunk and feed it a steak wrapped in dirty hippie clothes once a day. When surrounded by protesters, grab your cell phone, set it to video mode, and hit the trunk release.
I will update as more ideas come to me.