Most of my CS faculty in undergrad were great, but there were a couple like the guy you describe. And I wonder why in the world they took jobs as lecturers. If you don't have a passion for teaching, why take a job that pays substantially less than what you get in industry? CS isn't like, say, English where there aren't enough nonacademic jobs to go around.

In contrast, most of my faculty in medical school were terrible teachers. But there it made sense why. They were either there because they wanted to work at a large quartenary referral hospital or because they wanted to teach residents (not students).