Sadly, what the anecdote sheds most light on is Brother Nathanael's preference for vulgarity and patently insulting conduct...
I noticed that as well. He seems to be frustrated and/or looking down on these particular non-Catholics. He seems self-satisfied with his own station, and has a bit too much pride mixed in with his zeal.
Nevertheless, anyone who reacts this viscerally to the Cross of Christ -- it supports what the Saints have taught us, that the condemned soul throws ITSELF into Hell when it sees everything clearly.