I think we have a winner for "Most petty way to deny opponent's celebration"
In the second leg of the Peruvian championship final,, the home team was confident of a victory, having drawn the first leg away to their rival, 1-1. However, things they did not go their way, and they lost the second leg, 2-0 (and 3-1 on aggregate).
The opposing team however, did not get a chance to celebrate on their rivals turf, as moments after the final whistle, the lights in the stadium went completely out, except for the LED advertising boards. The general belief is that it wasn't a "power outage", but someone backstage furious that their hated opponents were going to celebrate the title on their pitch.
If so, they did get their wish, as the post-match celebration was cancelled due to the "power outage" (and as fighting broke out between rival fans).
Universitario left dancing in the dark to celebrate Peruvian title | Soccer | The Guardian
edit: Now that I think about it, this does have some upsides, in that it allows the team to officially raise the trophy at home with their supporters this weekend, but kinda unfair that they didn't get to celebrate on enemy turf.. I think before the next derby between the two teams at that stadium, they should be allowed to reenact the trophy celebration, complete with confetti cannons, etcetera.