"Ward Churchill is a posterboy for the lunatic right, but can it be doubted that if tenure and the expectation of academic freedom didn’t exist that far milder political expression than his and far more substantial scholarship would be under regular political assault? How many administrators would be able to stand up long to angry donors, threatening politicians, and astroturf outrage? What likelihood is there that media demagogues could resist the chance to brew up culture war? What chance is there that, against highly focused activists, stable political support for academic independence and integrity will be found? (The fight over evolution in public high schools is not exactly encouraging.) For all of its many imperfections, tenure still seems fundamental to maintaining the independence of scholarship and higher education."
Looked at another way, rights in a society which already enshrines democratic government are not so much about letting individuals do whatever they want as about preventing majorities from doing whatever they want. That's why the First Amendment was added to an already democratic constitution. You could have a democratic totalitarianism. This ties in to tenure because unlike, say, a contingent employee who is fired or otherwise forced out after a boss doesn't like something they said in a letter to the editor of a local newspaper, teachers - whether in college or high school - are required to speak out all the time about topics many find controversial. It is their job to seek and pass on truth irrespective of the passions of public opinion. Some have complained that the need to appeal to tenure committees makes academics afraid to be too original or interesting. Just wait until aspiring academics have to worry throughout their career about threatening anyone who could potentially make trouble for administrators.