Find someone that is a dead shot with a high caliber scoped rifle. This only works if the jerk lives out in the country BTW. If he is using a beam a couple of well placed shots into the center of the boom and he will have a very funny looking antenna. Or just clip the coax connection at the antenna with a shot or two.
Bad idea. Rifle bullets shot horizontally (even if fired at near vertical angles) will come down with enough velocity to kill a mile or more away. Plus, when the police retrieve the bullet downrange they can always match it to a particular weapon.
Small birdshot, OTOH, fired up into the air rains down harmlessly. And it's untraceable to a specific gun. Plus it's a whole lot easier to hit skinny antenna tubes with a shotgun than a rifle. So load up your 12 gauge with a No. 8 dove & quail load and turn that aluminum framework into something resembling Swiss cheese. The nice open pattern from an improved cylinder choked skeet barrel will totally destroy a gamma match when fired from the alley behind the bucket-mouth's house, instantly rendering the antenna useless.
I'm speaking hypothetically, of course, because I wouldn't know anything about any actual incidents. And any resemblance to any real events is purely coincidental. In fact, I'm pretty sure I'm just totally making all this stuff up.