One key reason for tenure is to protect academic freedom. I'm very interested in this notion that academic freedom and tenure are inseparable when 50 percent of the faculty don't have tenure. The conclusion I draw is that academic freedom doesn't seem to be compromised. Therefore, the two must be separable.
Universities are places where threatening or unpopular ideas can be exchanged.
The public will determine the line between the free exchange of ideas and trash. This system is self-policing if we let it be, but currently there is too much protection of colleagues for the sake of collegiality. To criticize your colleague is to put tenure and the process at risk, and therefore, your own position is at risk. We've accepted academic freedom at a philosophical level but not at a practical one. This has made the process unpopular with the lay public.