Perhaps one of the most infuriating responses, especially when repeated day after day by students, subordinates, or someone hired to do a job, is “I know.” When a contractor tells a subcontractor that a line of bricks has been mortared in place crookedly, and the mason says, “I know,” the initial response of any contractor is probably, “If you know that, why in hell didn’t you fix it?” So, most likely is the reaction of a supervisor or employer when an employee responds to a correction with those same words.
My wife the professor, who teaches classical voice at the university, must hear that phrase a dozen times a day, because, almost uniformly, when she tells a student that the student has mispronounced a word [and no, in most classical singing, you don’t get to choose your pronunciation; there is just one correct pronunciation], failed to sing in rhythm, or sung off the pitch, the student almost invariably replies, “I know.”
Do people use that phrase because they don’t want to admit their ignorance? Don’t they understand that, if they admit that they know better, they’re really saying “I know I’m doing it wrong, but I didn’t want to put in the effort to do it right.”? Or that they don’t have the skill to do it right?
The bottom line is that if you “know” it, fix it… or ask for help fixing it.