That's the million dollar question, doug; personally, I think they've all bought into the "me-isms" and "don't be judgmental" psycho-babble that the socialist educators have shoved down our youths throats for the past 20 years.
Those who don't comply (a/k/a those who have rational standards (based on something other than their whimful, subjective standards), think independently, and disagree with their behavior and ideas, are labeled "troublemaker" or "radical rightwinger".
The leftie liberals are selfish and prideful, unable to think critically or independently, are intolerant of anyone/anything different (which, ironically, happens to be extremely judgmental)....and what's worse, they are either blind to or find excuses for their own selfish, prideful, intolerant, judgmental, and shameful displays of behavior.
I have to say, Doug is not exagerating when he says that his bumber stickers are "fairly large". They are HUGE! and they are on a white background attached to a black vehicle. He 'sticks it in their face' (I love it). I can see how a stone-cold liberal would want to execute a reaction, but having children flip the bird on the freeway! That's a little much.