think of the word "berate" (to scold/rebuke)--- vitu(p)BERATE
vituperate. sounds like vethu po+rate i.e to rate someone negatively and condemn/criticise them
Picture a person finding fault with another. He is shouting at that person and beating him over the head with two berets, one in each hand. (vit) WITH TWO BERET
vit sound like fit of perate(parade)
Imagine a *bitter(vitu)* + *parade*(perate), where one angrily blame each other or insults each other.