I can see some arguments on both sides. Tenure was established by, and for, white men who in many cases were perpetuating the kind of system that women and faculty members of colour were trying to break into (and which persists, in not-so-small pockets of academia too).
But the security of a tenure system is what allowed members of those groups to gain (and maintain) their foothold in academia. To some scholars of the old guard, tenuring women would have seemed an outrageous detournement!
In university systems where tenure does not exist (or the UK, which has had a "defacto" tenure system - see the discussions on recent dismissals - attempted an otherwise - of senior faculty at KCL for some views on how that's worked out), the culture is different. Better? worse? I don't know.
EDITED: after our comment exchange below, Heinrich forwarded me a link to Brian Leiter's take on the tenure issue. With this, I find myself in total agreement. Particularly with his two points about the current weaknesses of the US system: Inadequate protection and support for the untenured, and unwillingness to dismiss the tenured even for good reason.
This is a key point - the few academics, who are a minority but who make the news for outrageous behaviour end up swaying attitudes about the concept of tenure, and the public perception that it is a guaranteed job for life for people who behave like jackasses. Here some people seem to equate tenure with free speech, too - see Churchill, Ward. I have witnessed quite active debates over what "academic freedom" means; whether simply the right to research controversial topics, or the right to teach any subject matter, in any form, and speak out on any issue under the sun. Some clarification from the AAUP would really help - academic freedom should mean freedom to pursue academic research, not freedom to do absolutely anything because you are an academic.