Yosselle, You’re just not getting it. There are two Rabbonim in this town with exactly the same name. One of them had a nickname, presumably as a child, which for the purposes of this debate, let’s say is Benny. So people of the town, who wish to identify him, refer to Reb Benny, in addition to his full and proper title of Reb Binyomin Greenberg.
He doesn’t choose the name Benny, it is used for convenience by the people, in a respectful way to differentiate him from his namesake.
Capisce?