Don't know how it could be protected if it doesn't exist, but if it's protected I would definitely not be suggesting removing it.
I would point out the irony of protecting non-existent creatures, though.
I would point out the irony of not reading the thread and knowing the OP's premises have been shown to be false. You are playing up a patently false claim.
First, mountain lions do exist. Second, they have existed in the recent past in WI. Third, WI has laws that protect them. Fourth, this is because they travel long distances and easily repopulate previous ranges. And Fifth, WI DNR recognizes and has numerous documented and verified examples of mountain lions in WI in the last several years.
Not only does the creature exist, it exists in Wisconsin. There is no irony about having laws to protect it.
With that said, the OP's mountain lion does not exist in WI. It exists is MI and cannot be covered under WI law until and if it ever enters WI political boundaries.