The NBC Symphony was a very good Orchestra. This was Toscanini's normal routine in rehearsals and I have heard that the guys in the recording room liked to watch the needle "redline" when he did this. It was a different era and it would certainly not pass in an Orchestra today without repercussions. You gotta give the man credit though. During the build up to WWII, Toscanini was in a posh restaurant in Rome and began an abusive tirade against Mussolini and his fascist regime and nobody in the restaurant ratted him out.
One of history's musical titans, Maestro Arturo Toscanini had the ENTIRE repertoire of western symphonic music MEMORIZED! He never had scores before him when in live performance, using them only during rehearsals.
Composer Richard Wagner's wife claimed that only Toscanini conducted Wagner's works as they were meant to be heard. If he displayed impatience and a fiery temper towards his musicians he certainly knew what perfection meant in musicianship and we can rest assured his orchestras were the better for it. On a humorous note, the great conductor once stopped during a rehearsal and snapped at his female cellist: "Young lady!"..."Such a beautiful instrument between your legs, and all you know how to do is scratch it!"