Why wouldn't you 'cherish' a warranty that's bumper to bumper? Not all performance mods will void the warranty. It's up to you to educate yourself on what does and does not void the warranty. It's not the dealer you should hate - they are happy to do work on your car, but they have to get paid... by you or GM. If GM declines the warranty work because you as the owner voided the warranty that's not the dealership's fault.
"Being persistant and never giving up may not always get the job done, but it just may annoy someone else enough to make it worth your while."