For those that are interested in the original post...
There are times when verbal obstruction is a proper call. Back, back, back to the runner at 2nd is probably not one of them... runner ought to be able to tell the difference in location of his coach at 3rd and F6 that is behind him. Further... Back, back, back doesn't create the obstruction (impede the runner); there must be some response from the runner... if the runner does nothing different, there has been no obstruction and hence no need for an official's call.
Now... times when the call would be appropriate... Shortstop yells for runner to slide coming into 2nd and then after the slide gets tagged out at third, or players in dugout yell for runner to slide at home and in either case the runner gets injured because of the unexpected need to slide... Obstruction is a proper call and an ejection is likely relevant too for the injury.
PS. It is truly amazing how some pitchers can get a pitch through the zone and have it bounce in the dirt before it gets to the catcher. Obviously could see it in a slow pitch softball game but how does one throw it at 70 MPH and make it drop 18 inches in the next 3 feet? I've seen them and I didn't call them strikes (I wanted to), but it is still amazing.
Life is short, my friends. Play ball.