Hate is also a kind of love standing upside down. It happens that you can forget your friend, but you cannot forget your enemy. The enemy haunts you more than the friend. You think more of destroying the enemy than helping the friend. The reason is that love is a thesis -- simple. Hate is an antithesis -- it has become more complicated. It has become negation, and negativity has an attraction -- for many reasons.
One is afraid of negativity because you cannot hate someone without creating a wound within yourself. Nobody pretends hate. It is always authentic, because why should one pretend hate? -- It hurts.
People pretend love; they may not be really in love, but the very idea that they are in love is soothing. So love can remain superficial; but hate always goes deep -- it cannot remain superficial. That's why one becomes more concerned about the enemy than about friends.