Once again, I can't see the video, so i'm just going on what is written.
Finally, while it's certain the the calf was injured, since he was partially weight bearing on the leg, we have only the maker of the video's word that the leg was broken. Should the calf have been examined and given medical attention? Yes, absolutely. Do I believe all the claims of the folks who made that video? Heck, no.
Generally if it is a clean break on a calf or sheep, you can see the leg flopping around - If they are just not weight bearing then it may well have been something less serious.
Also - It is bl**dy hard to catch a calf on it's feet, even a three legged one - it may have been necessary to get it into the yards out the back to provide proper assistance.