Sounds to me like he could be taking what you said about your drinking as implied criticism of his own. He could also be fearful of losing the closeness new has through you being a drinking buddy as well as a sibling.
Whatever his reasons, you know where he's coming from now so can adjust your expectations of him to protect yourself from being surprised and hurt by it next time. (There's a good reason for AAers using the serenity prayer like they do asking for the serenity to accept what we can't change -other people) and the courage to change the things we can (ourself, including our expectations ) and the wisdom to know the diffrence).
Acceptance isn't about whether they are right or wrong. Just accepting that's how they are and we can't change that. What other people think of us really doesn't need to be any of our business. The alternative is letting ut niggle away and likely cause a horrible toxic little resentment, and those things are toxic to our recovery.