I know some Leftists. They're not Leftists of the loony, venomous, conspiracy-theory variety who hang out in the comment threads of Left-wing blogs. They're you're garden-variety, conservatives-are-mean, government-is-good, Bush-is-bad, pull-out-of-Iraq, global-warming-is real, Social Security-Medicare-and-universal-health-care-are-necessary type of Leftist. But they're generally quiet about it, unless they're talking to each other, in mutual support.
The thinking of the Leftists I know was shaped by "educators" and is constantly reinforced by selective (i.e., biased) reading, listening, and viewing. In other words, they have never matured mentally. They're stuck on the themes they were force-fed before and during their college years. I would say "stuck on stupid," but they're not stupid -- just ignorant and mentally lazy.
The hard part is: Most of them are nice. So, it's hard to dislike a garden-variety Leftist, in spite of his or her views. Of course, it will be a different story if any of them starts hanging around the comment threads of Leftist blogs.