What would you say?

Surgery is seen as the easy way out by most people.  I keep my surgery pretty much to myself

I think you've said everything you can say at this point.  The most you can do now is what you need to do for your health and to demonstrate to him that you made the right choice with your actions and your success.  

Everyone doesn't need to agree with us or support us, even though it would be nice!  The only one who needs to support your decisions is yourself.  :)  

Also, I think it's important for us to remember that WLS is a decision that we got to make with plenty of time and consideration.  When we tell people about it - they don't have the benefit of the time that we had to come to terms with things.  So maybe, over time, your brother will come around.  

it is a very common reaction , but many people will change there mind if you give them time sometimes having them go to a support group meeting or to see your surgeon may help

Success - maintained over time - is going to be your best "argument" with your brother.  Don't try to fight his attitude with words; don't try to reason with him; don't try to explain.  That's all a waste of time.  You'll have to prove it to him with your actions.  

That means you'll need to use ALL the tools in the toolbelt to make sure you are successful - surgery is just one.  If you need therapy, get it.  If you have disordered eating, go to Overeater's Anonymous.  Go to your support group meetings.  Make sure you find exercise you enjoy and do it!  

When he sees your weight loss and that you are out there being active, eating healthy and living life, he'll hopefully change his tune.  But it could take a couple years before that happens.  In the meantime, don't waste any emotional energy on what he thinks.  What other people think of you is none of your business :-)