This journey is HARD. Pre-op diet and post-op diet especially are difficult, plus if (God forbid) you experience a complication, you are going to need support. My psych eval included ensuring I have plenty of support at home to help me with my recovery from surgery and help me stay on track. As much as it would be awesome to say "Piss off!" and just do what you want anyway (LOL) you have to live with this guy and let's be honest, that ain't gonna work.
Your hubby is very wrong that this is the "easy" way out. As someone who's done WW, and lost and regained the weight a few times, I can tell you this is just as difficult. It's a hard decision, it takes will power and dedication, just like any other lifestyle change you make. He needs to be educated. Suggestions:
Would he respond better if you wrote him a letter explaining why you feel the way you do? Sometimes if people see it in writing, it resonates better.
Do you have a support group through your surgeon's office that you can take him to? Would he go to a meeting?
Don't take this the wrong way, but a mediator or therapist could help, too. There is NO shame in it-- sometimes having someone in the room to push the conversation in the right direction (meaning, understanding each other on a deeper level) would be helpful. Just throwing ideas out there.
I would also provide him information on how safe the surgery is. I'd be willing to bet he's afraid to see you go under the knife! Completely reasonable to be afraid, but the surgery is very safe, generally. Especially if you're young (you look it) and have few health issues. If he wants to keep you around for a long time-- prevention of health issues is best!! That's why I did it.