I realize that fights may, and probably will break out a these joint practices, obviously disrupting what the coaches are trying to get done. But overall I see them as a positive. Our coaches are new and trying to implement new schemes/ideas. The more opportunities they get to try them out against other players who don't them the better IMO.
Also getting to compete against other teams/players can intensify things in practice, besides the fights. It can cause some players to feel the pressures of a real game and that can bring out the best and worst in some players. And IMO it's good for the coaches to see how their players will react in those situations before it matters in a game.
There is also an added element of team bonding that can occur if and when there are any altercations. Team mates, who may not be the best of friends at camp, will defend each other against a common foe, which creates respect and friendships. Which helps the team become one.