Oh, so by "uncle" you mean a family friend and not a blood relative? If so, that's still really strange, because I've heard of people declaring friends/non-relatives as Ontario ties but they've never been asked for this requirement. Maybe you just caught a strict officer by chance.
I suggest you either have your uncle provide a letter that he's not willing to share his bank statements with you and that OINP can contact him directly if they have any concerns about this sponsorship, or you don't mention this "uncle" at all when you resend your application...there have been plenty of nominees that did not declare people in Ontario as ties.
Yes, I got my nomination from OINP, timeline in my sig, but my relative is a direct blood relative so they didn't mind sharing their bank statement with me.
I still believe you have a good chance to fix this.