First, there is no grammatical mandate regarding the tense of the events of the story and the commentary. This question is one of stylistic strategy, so there isn't exactly a right or wrong answer here.
That being said, I would recommend writing the bolded segments in the present tense, as the commentary comes off more powerfully; as it is currently, in the past tense, it sort of awkwardly teeters between the events of the story and a more timeless commentary on human nature.
I suppose one consideration would be who is making the bolded statements. Is it the main character breaking away from her (or his) recounting of the story to comment to the reader or is the character narrator thinking these as thoughts in the past—while the events are taking place? Is it the author making these claims?
It would only make sense to keep the commentary past tense if it is being made or thought during the events, or if the narrator him/herself is recalling this story in the past (rare, but certainly a possibility).
Hope this helps!