Cyclists should slow down around pedestrians. No more complicated than that.
Cyclists should also not physically assault dads.
Slowing down isn’t a universal answer. Define slow. I rode at an average of 15 mph, and got passed constantly. Was I slow or fast?
I started off saying the cyclists shouldn’t have reacted the way they did. But that doesn’t change the math. If the parents had recognized the inherent danger of multi-use trails (because they are inherently dangerous, lots of random going on out there) and done a better job of controlling their the entire incident doesn’t happen.