His friendship with Felix was set up in earlier Bond movies, albeit poorly. I don't thin his snapping was supposed to make sense, because rarely does one event only drive someone to do what Bond does in that movie.

License to Kill does things I think are a big no-no in a Bond film (describing the history of Bond too much, getting too psychological with the character of Bond beyond his professional role), but they needed to shake it up after the very boring Living Daylights and I like the idea that Bond just doesn't do his mission for Queen and country. It's the closest the series gets to exploring how fucked up a sociopath like James Bond would actually be, without going too far with it. It's the most underrated Bond film.