I love diet, caffeine-free soda. Just figured I'd be the sole opposing voice on the matter.
There's a book I really like, Wildside by Steven Gould, where to avoid spoilers I'll just say that a group of teens are cut off from the amenities of modern civilization for various periods of time. The main character loves caffeine-free diet cola. He craves it like nothing else. Which annoys him, because as he puts it the stuff is pretty much useless. "I mean, it doesn't even keep you awake!"
I avoided caffeine entirely for 25 years or so, as when I was in my late teens I discovered that it made me quite ill - as in nausea and vomiting and similar unpleasantness. Just a couple of years ago however, my husband brought home some diet cream soda from the store and I got into the habit of taking a can with me to work every day. After a couple of weeks, I finally noticed, in small print on the can, the words "contains caffeine." I cautiously experimented with other caffeinated drinks and sure enough, I'd outgrown my caffeine problems! Exactly when it happened I have no idea, as I'd been very religious about avoiding the stuff.
So I've experienced both pro- and anti-caffeine dictators.
I drank caffeine all through my childhood and into my teens. My mother avoided it, but not strenuously. When I got to college I started having some nasty symptoms that frankly scared the snot out of me, and I couldn't figure out what was going on because my diet hadn't appreciably changed. My mother suggested I cut out caffeine, and that worked. It had happened to her the same basic way, but not until she was in her mid-20s, which combined with the fact that I'd never had any trouble with it before explained why she hadn't warned me about it.
So I switched to caffeine-free Coke, went through a week or two of withdrawal that really, really sucked, and got on with my life. About ten years later I started drinking the occasional regular Coke, with no ill effects, so now I'm back to the good stuff and going strong. The only side effect is to my waistline.
I've never encountered any caffeine dictators, pro or con. When I was drinking water or Sprite when out on the town I'd explain that I had troubles with caffeine and that was met with an "oh, sure" type of nod and occasional commiseration. No one's ever given me guff for not drinking coffee or generally not drinking alcohol, either. Considering some of the stories I've seen here over the years, I'm a lucky man.