If you submit a review for a paper and all it says is, "We already know this" (or something similar) but don't provide citations you should be banned from reviewing papers.

If we already knew this, do you think I'd've written it ya twit? Why don't you check my lit review where it shows the existing research _doesn't_ already know this.

Nonsense.

(Reviewer 2 recommended R&R with minor revisions....)