Tenure is the worst idea ever. It is essentially saying that it doesn't matter you are unproductive and a waste of space, you did something really good in the past so you are now in the Club now.
This is only partially true. At the very least, most people who make it to professor are crazy by then, and just continue in there never-ending fight like ever before.
Additionally, tenured professors will be bullied by the administration if they underperform. That can get very nasty.