They should get a bucket with a lid or similar container and put it underneath while cutting close if not the branch and then figure out a way to dispose of it/them.
No mess and no problems with eco-warriors. Way more humane. Professionals usually just spray toxic junk at them, don't they? This way seems to suck less erm no emphasis on the less
Well, actually, hornets do not pollinate. They are carnivores - eating other insects + my bees. But I agree with you - I hate to see them destroyed without good reason. Hornets don't attack you if you let them be.