That really wasn't appropriate for your BGO to say and, quite honestly, I think he has an inflated view of his importance in the process. As noted above, I once had a candidate lie to me multiple times and I then made it my mission to ensure he didn't get an appointment. It took a lot of effort -- and the backing of my Area Coordinator to whom this candidate had also lied -- to get it done. But this was a rare occurrence and the ONLY time I've done this in more than a decade.
It is very hard for a BGO in a 1-2 hour interview to trump a candidate's objective record (grades, scores, ECAs) and the recommendations of teachers who knew him/her for an entire year. And, a negative review that isn't supported by facts won't carry any weight at all. I think a lot of us wish that we could keep certain candidates from receiving appointments, but if wishes were horses . . .