Write a letter to the editor or have an interview with a local newspaper. Try and tank their public image?

Start feeding birds in the parking lot next to management's cars until the birds regularly poop all over them. Put vaseline or motor oil on the inside edge of all their office door handles. Swap all their pens for dead ones - when they replace them, do it again. Mysteriously have the printer/copier go down every day. Contact an orphanage or children's charity in the company's name and promise an enormous donation and organize a massive publicity event around it.