Dear Ms. Price,
As long as your son is doing what you say, you can very safely ignore the talk. Too often we get off track by pursuing such talk - it doesn't pay off. It deserves the same amount of attention as does a two-year-old's noisy, non-destructive tantrum: none.
Try ignoring it when he does it and give him specific positive praise when he does not do it. However, when he does it and a little later comes to you and wants to do something such as watch a video, tell him no because he did not act properly before when he talked back to you. Cause and effect, along with positive praise for good behavior, should do the trick in a couple of weeks.