No shit the reasons are obvious. Why are we acting like this is the da vinci code? Give yourself a pat on the back for knowing this underlying message. It's accumulated, doesn't excuse Oda's depiction of his reaction to her betrayal.Character development and depiction is a topic worthy of depth?
The reasons are obvious, and yet you still go about wah-wah'ing about how it was "Pudding, just Pudding, all Pudding, look at what he's doing over Pudding."
Like I already said, it was unnecessary we already got a visual of Sanji being broken down. The extra bit was done for theatrics, not some "underlying message" like you love to claim.