- Buy put options or short-sell stock -- that is, bet that the stock will go down -- of the offending companiess (just call a stockbroker and say you want to buy put options)
- Put pressure on the FCC to deny license renewal for the offending companies by writing a letter to network affiliates stating that the company is not serving the public interest
Of course, people can also boycott the sponsors of the offending media. For example, here is a list of Fox News' sponsors. And more ideas for boycotts are here.
And for those who already own shares of stock in an MSM company, another option is simply to sell them. If enough people sell, that will drive the price down and hit the MSM in its bottom line.