Loving everyone is really about yourself more than the other person. If you have love in your heart towards everyone then you will be able to live your life happy and not stop to be vex, angry or full of hate.
I try this but it is terribly difficult for me. I've seen some pretty ugly things done by some pretty evil people in this world and I can't bring myself to love them. Heck, I can only imagine what I'd do if someone hurt my kids… there'd be no love. So this is something to strive for I guess, but you'd have to be a saint… which is why they are saints I guess.