If they're going to take it off easy enough at the end of the rental, seems like it's a great way to get yourself some "free" insurance. If something happens to the car, the insurance you didn't want is already there (in which case you keep the insurance at the end). If nothing happens you get to tell them you didn't want it and that it should have been removed.
They'll just pull out the contract you initialled and it'll be all over.