for those of you who dont know how a chain link fence works:
you drive between the posts (figure 1) and the fence ties (figure 2) hold the fence onto the posts. if the fence ties arent there in the first place, or you break them while driving thru the fence it gets lifted up by the car, you arent going to knock over the posts by hitting just the chain link part because the posts are cemented into the ground.
theres this thing called gravity plus the fact that theres other parts of the fence still tied on that brings it back down to where it was before. the cop either was too stupid to drive thru or he just didnt want to scratch up his car.