On the surface, it might not seem worth it for a guy to get beaten up over a turtle. In this case, however, the nature of the acts flags these three as likely sociopaths who should warrant extra scrutiny when being checked out in the future.
If these were people killing the turtle for food, it wouldn't be worth getting involved, even if sea turtles are protected by law. However, someone who tortures animals for fun eventually winds up torturing and killing people for fun.
The turtle was a dress rehearsal. A year from now, these black hoods will be playing the knock-out game with elderly white people as targets, or torturing some kid with lit cigarettes because he wears a MAGA hat. In fact, I would wager that these Sons of Obama have already played the knockout game in their neighborhood.