NONE of the tellings of the story is the Truth. The point of RASHOMON is that even when we mean to tell the Truth, even when we are not conscious of altering the Truth(lying,embellishing,withholding,etc.), we cannot achieve absolute truth. We can only achieve a truth that is subjective because we only perceive a portion of reality and that portion is "filtered" through memory, personality, cognition, language, etc. When Priest exclaims: "I have seen hundreds die like animals but THIS is terrible", he is referring to this inherent ignorance, this human limitation.
Towards the end, the Wood Dealer and Priest hear the cries of an abandoned infant. Wood Dealer decides to adopt the baby even though he has several mouths to feed already. We see him smiling(the film's sole smile),walking away from Rashomon gate, baby in arms. The film proposes that human suffering and ignorance, which is a given, can only be abated through love and self-sacrifice.