A.M.
A couple of things I can think of
1) Maybe he wants to do it himself. Try some canned or frozen carrots, the kind that are in tiny cubes or other finger foods like cherrios.
2) Maybe it is just his way of asserting his own individual wants as babies start to do at this age.
Either way the American Academy of Pediatrics says that most of a baby's nutrition should be coming from breast milk or formula until at least 12 months. So it may not be worth the battle now. He will can still get all his nutritional needs met through his milk/formula. Good luck.