Yes, and the GSP is as good a road to avoid as any with the possible exception of the New Jersey Turnpike.
Look up "Avoid area" in the S&T Help for instructions.
You can select a small area that would include the on-ramp or intersection where the road 'begins.' You may have to do this more than once if the route then puts you on the dreaded road further along. A few tries should get what you want.