My answer may sound like one from a politician: Taking that backing off would definitely be safer, but you might want to leave it on.
Reasons to take it off and replace it with regular dacron-type backing: The spiderwire stuff is so strong, if it gets looped around your finger while the fish is running, it actually can lop off a finger. (picture a superheated wire cutting plastic or something like that) The stuff also seems a little more prone to digging down into itself than standard backing, but with some care, this can be pretty fully avoided.
Reasons to leave it on there: There is no other way to get the maximum backing length capacity on a given fly reel. If you are going to be after huge bones wading on foot, having as much backing as possible might be wise. Some would say that 100 yds of backing is plenty for bones, I would say 150 yds is a pretty safe amount to have to work with. However, if you hook into a Permit, a Jack, or something else large with that 8wt rod, 150 yds may get you nothing more than cussing and frustration.
So, its your call.