Let me qualify this...
Mankind only thinks they know what love is. And even if they genuinely love it is without an absolute love on which to anchor all love. The same as it is with Truth. Truth without the basis of absolute Truth on which to anchor all truth is not genuine truth.
God is love.
And we are to love one another.
In fact, the secular version of the Golden Rule (which is not in the Bible) "Do unto others as ye would have others do unto you," is a hopeless, baseless version of "Love thy neighbor as thyself."
Do unto others as you would have them do unto you is simply trying to get along in the world. But love your neighbor as you love yourself draws us out of the Me mentality... and at the root of most of the evils in the world today is Self... it began the down hill slippery slide with the Me generation and is now in the Self generation... with kids killing kids in schools and mothers drowning their children to please their current lovers, and gazillionaires stealing the ability of the average citizen to earn a living and provide for their families, with welfare type programs being exploited by the poor to get their electronic gadgets while getting baby formula for free...
And there aren't enough atoms in the universe to satisfy the lusts and desires of 9 billion selfish people.