Maybe Foligno said something about Smith's mother. Maybe something happened earlier in the game between those two. Who knows why they fought. There are plenty of fights during games that are blowouts, and it always takes two to tango. Smith didn't do anything selfish by fighting. Selfish would be a retaliatory penalty that costs the team a powerplay goal. Smith wasn't thinking about getting potentially injured, nor should he, so I wouldn't call it a selfish decision because he got hurt. It just happened.
This I disagree with.
There was nothing the team could have gained by Smith getting into the fight The game was already comfortably under control in the Wings' favor. Smith, on the other hand, could have repaired his own damaged ego (or his mother's if that's the case), or seeked retribution for a hit he didn't like, but those are personal reasons to fight that have nothing to do with the team's odds for victory. So in this case, the only one who's getting any potential benefit out of this is Smith, and its an entirely emotional benefit.
As for risk, well there is always a risk of injury when getting into a fight, and everyone should weigh that risk against the potential benefit when choosing to partake. There is also the guarantee that your team will have to play without you for the next five minutes, which is a more serious situation when the fighter is a defensman, becuase there's only six of those total to begin with. If you're one of the folks who believe that fights can be a rallying point to boost team morale and get everyone more engaged in the game, then there's also the risk of firing the other team up, and potentialy losing a game that your team was winning. So in terms of risk, Smith is risking his health, he's risking his team losing control over the game, he's putting Babcock and his teammates in a tougher spot because they have to pick up his slack while he sits in the box, and if he happens to get injured in the fight (which he happened to get injured), then Babcock and his teammates are in a tougher spot for the next several days, instead of just five minutes.
So lots of risk and disadvantages that the whole team has to carry, so Smith can resolve a personal vendetta that he has in the waning minutes of a game. I'd say that's quite selfish.