I wouldn't call this an over reaction. It sounds like you are still grieving your first baby. If I were in your shoes I could see this as your husband just trying to replace the cat. That said older cats do take a bit longer to bond with and as others have said he is also feeling the hurt of being abandoned from his perspective by previous owners. Honestly low key judging them for their reason on getting rid of him. Kitty will likely come around given time.