A.J.
Let it go!
Don't try to make him engage. Don't allow hostility, but trying hard to make him care is giving him attention for negativity. Let him be. A 2 1/2 year old boy and a tiny baby don't have much in common. My 2 1/2 year old plays with baby sis, but she's 1, walks, wrestles, and he's sort of copying his older sister and doing it for praise at times. Sometimes he yells at her (when she screams in his face and he's napping for example) or ignores her. No biggie. It will improve over time. Just give him lots of love when the baby is napping and you're not holding her.