It shouldn't be hard to understand why the old man would act in such a way.
#1 He was blatantly 'farting' in her face, anyone with an iota of self respect would want to tear him up.
#2 Humans dont always have the capacity to change their minds once they have been made up, even when contradictory facts are presented.
#3 He was in a state of mind (anger) especially not conducive to listening.
#4 He's an old man, so even less likely to act rationally. perhaps he didn't even understand what was being explained.
We are not rational machines, and we cannot switch our emotions on and off on command.... but I'm sure any getbigger would have handled it perfectly reasonably
