Sure, tearing off a small part of the last slice of pizza means getting your grubby hands all over the part you're not eating, but taking the entire last slice is just rude. This is a no-win situation.
Who's worse? The person who sarcastically calls out people for not recycling, or the person who goes through the trouble of counting the EXACT number of steps to the recycling bins, and prints that info out on a photo of Dwight from "The Office," yet still refuses to recycle? It's one of life's great mysteries.
Is this note asking why someone ate part of the cupcake? Or why cupcakes exist? Or maybe it's asking why ANYTHING exists. Whoa. Sometimes it just takes one word and a partially-eaten cupcake to really make you think, you know?