I'm a tree-hugger and I also recommended "squishing it." I hate killing things, but some things just don't need to co-exist with me. Fleas, mosquitoes, flies, cockroaches, bed bugs, slugs, ground bees or yellow jackets, potato beetles, etc. They are all "cool insects" and have a purpose. They can exist elsewhere but once they take up residence inside my house, on my pets or in my garden, if there is no non-lethal alternative, they get dead.
Besides as Chuck points out, hornworms have very specific hosts. Relocating them just means they'll slowly starve to death and won't mature, unless you grow a separate garden to relocate them to. I think a fast demise is kinder, really. And squishing them is definitely better than drenching your yard with Ortho products.