Why "fun" is a zero-sum game.
The Burden of Intellect
It is lonely at the top. When you are the only person at the table who truly understands that strictly adhering to the "Farmer Gambit" in Agricola is the only way to play, others may call you "rigid" or "unfun."
They are wrong. You are not rigid; you are optimal. And they are not having fun because they are losing. Your winning is the fun. The fun is conserved; you are simply hoarding it all.
Mercy is an Insult
To let someone win is to treat them as a child. Do you respect your friends? Then crush them. Annihilate their hopes. Block their routes. Steal their resources.
"I destroy my enemies when I make them my friends... by defeating them so badly they ask me to teach them how to play." - The Alpha Gamer
The Victory Lap
Is it enough to win? No. One must win in a way that resonates through the ages (or at least until next week's game night). A true victory is one where the opponents nod in silent, terrified respect.