"Debridement" is the physical removal of soft (plaque), and hard calcified (tartar) deposits from the teeth. Rinsing with mouthwashes, including peroxide, will likely not harm you unless grossly overdone, and will likely benefit you. It will not "debride" your teeth of tartar, and not really do a very complete job of cleaning plaque.
I don't know why so many people are so dead set against taking the 2 minutes out their day to just do it properly with a good brush and flossing. Have you ever tried to get your car really clean just by spraying water on it? I find I can spray 'til the cows come home, but if I don't take a nice soft wet cloth to it, there will always be some of that grimy film still on the car.
As far as why your dentist did not want to engage you in a long conversation of the magic of your "debridement", he probably has found that he has better uses for his time than trying to engage in such a conversation with someone who is convinced he/she knows more about the profession than he does, and is convinced that any disagreement with this miracle cure is based upon greed, rather than evidence seen with his own eyes.