Instead of wasting time with protests that won't be televised (barring a few disgruntled fans) or doing anything criminal, why doesn't each and every fan pick up the phone and call an investment bank every day to inform them that if they find a buyer for United, the fans would publicly support the new buyer?
Be polite, inform them that United is a listed company, whose data is publicly available and that its not being run well. Make multiple calls a day to different investment banks. It will cost you nothing but your time and the price of a phone call. The transaction fees are paid by the buyer or seller depending on who the banks represent.
Investment bankers are looking for ideas all the time. Imagine if each bank gets a 100 calls a day, for 3-4 months ... there has to be an enterprising banker who can leverage this opportunity (through the wealth management/buyout teams). The media will definitely report on this. As a starting point, you only need to focus on a few banking/wealth management centers:
USA: NYC, Boston, Chicago, LA
Europe: London, Amsterdam, Paris, Zurich, Geneva, Monaco, Dublin, Frankfurt
Asia: Singapore, Hong Kong, Shanghai, Beijing, Tokyo, Mumbai
The best thing about this is that most of the large banks have multiple branches across every city, many who compete within the firm for deals - its a total dog-eat-dog business. You can literally pick one bank and make cold calls to all their branches in a day.
Check your local laws on cold calling. Don't do anything illegal.