As long as he's been that way all year, then he's right on.
This is BU's call all the way.
He won't make a call unless, he has one to make.
Now, you say "BU was behind the pitchers mound". Do you mean that's where he started or where he was when he made the call?
Umpires call what they see, if he indeed was behind the mound, then he may simply have missed it because of the distance/angle. Regardless, he saw what he saw and made "his" call.
You had your view and saw what you saw, could anyone convince you to change your mind?
Exactly.
Had you gone to BU, perhaps he could have been convinced that he may have overlooked something.
Something like; "sir, here's what I saw, I could clearly see the runners foot several inches from the base when the play was over. Would you mind asking your partner, because I'm sure he had the same view I did". Or something similarly civil.
And what if you hear; "yes I saw the foot off the bag, but because of lack of control by
F5 on the bobble, the runner got his foot in, and is safe. But thank you for asking, play on".
Okay, his answer in short is "nope, I had that all the way".
Play on, it's over.
Or, and don't count on it, unless your plea is a good one. Say he goes for help. He'd go to his partner explain what he saw, perhaps your opinion, and ask "is there anything I didn't see there"?
HP say's, "I saw the whole play, except I could not see R2's foot, so, no, I don't have anything to add". It's over, play on.
Never "Time, Blue, (while flailing towards PU) can I get some help on that ridiculas call"? P.s. I am not insinuating anything here about anyone, just comparison only.
After time out has been granted, always go to the umpire that made the call, simply state your case and accept the response.
The PU stated, "that's his call", did you enquire of the BU?