On similar hard to peel backings, like some reflective tape, I've used a sharp razor knife on the corner of the edges. Use scissors to trim the end of the tape a little if the edge is mangled. It takes a few tries to get the blade in between the backing and the tape. Next, hold the tape by pinching the tape between the blade and your finger, then peel off the backing.

But if the backing is so bad that it just rips, then this won't fix the problem.