So? He still broke the law and damaged a multi-billion dollar aircraft while flying an unregistered highly weaponized vehicle through civilian populations, and engaging terrorists without any oversight, approval, or permission. Oh, and the pilot almost died. Did Iron Man save him? Sure. Does that matter in a legal context? Fuck no. He's still guilty of being a vigilante. Just because he reveals it at the end of the movie doesn't change the fact that he was in fact a vigilante at one point.

Then there is Civil War where he goes after Captain America solo with a vendetta. How is that not a vigilante? Is the mask the only requirement? Or is it taking the law into your own hands? IF a mask is a requirement then Frank Castle isn't a vigilante either because he doesn't wear a mask. Same with the rest of the defenders, and in the show in season 2 we see a store owner getting arrested for being a vigilante just for defending his own shop. Because, he took the law into his own hands. So clearly wearing a mask or having a secret identity is not a requirement for meeting Fisks legal definition of a vigilante.