Harsh, yes. But, as Michael said, it was "life and death." I think he felt he owned Tom an explanation of why he wasn't entrusting the family to Fredo. I have a feeling that Tom was closest to Fredo following Sonny's death--he sure wasn't close to Michael.
Ntra la porta tua lu sangu � sparsu, E nun me mporta si ce muoru accisu... E s'iddu muoru e vaju mparadisu Si nun ce truovo a ttia, mancu ce trasu.