There be monsters among us, beside us, all around us. Not just any monsters, but particularly nasty and vicious monsters that can adapt their modus operandi to foil all but the most crafty monster-hunters.
Look to your right or your left. Chances are, if you're in public, that you might catch a glimpse of one of these beasts, snarling and snapping at all who come within reach. Careful! You might lose a limb or even worse, your life!
People just find it so hard to be nice anymore. If it is true that humanity is basically good, that goodness is covered under a thick layer of selfish and irritable sludge. So many people lack the basic virtues of compassion, patience, trust, and friendliness that in many places, it is nearly impossible to establish human contact.
Of course, there's stress and anxiety in everybodys' lives and that's just the human condition. How much easier though to squeeze out a smile or a greeting than to snarl and act superior when everyone actually knows better.
There's a concept that life, the universe, or whatever you choose to call it, is like a mirror. Look at life and curse and life will curse back at you. Look at life and laugh and life will laugh with you. Look and life and smile and life will smile back.