remove staple without damaging NM
For those eavesdropping and who don't have enough working room, I would think about cutting additional holes in drywall to get at the staples instead of risking damage to the cable and having to string a new cable. Since you don't have to actually cut the staple, other kinds of pliers such as long nose could be used if necessary.
If necessary hold a screwdriver shaft or nail on the stud next to the staple to get additional leverage for pliers.
If the staple won't come out completely by lifting from the side, keep in mind you only have to pry it up enough to get a screwdriver or other prying tool under its middle without gouging the cable.