Pointing out areas for improvement is neither "eroding confidence" or "sabotaging career". The goal is to help YOU understand your weak spots, and correct them, and skills which are not central may still be important-to-essential. Part of a mentor's job is to help you see what matters more than you think it does.
I suggest you take the feedback calmly, give it due consideration, and work to improve the targeted areas whether you think they're necessary or not.
If all else fails, ask the manager whom you will be under after the reorg if they'd consider starting now as your mentor.