Dissenters, especially those who are active in their dissent could be delegitimized in order to take away their ability to be taken seriously by the public.
How it works
Mocking, or pointing out hypocrisies. Ignoring the message of a protest and focusing instead on the individual or group who are protesting.
This is a tactic often employed by political pundits and commentators. Here is Talk Radio Pundit, Rush Limbaugh, engaging in some activist delegitimization: http://www.youtube.com/watch?v=tKthEvX2luQ