I think it's not really reflective of reality.

While 99.95 of people think that a growl is a dog's primary way of showing aggression, it really isn't. It can be indicative of fear, aggression, or various other bad situations- but the real, PRIMARY warning signs are non-verbal in nature. I suggest you read "The other end of the leash", which is written by a dog behaviorist who specializes in aggressive dogs. As a short summary (read the book, really!), the primary cues are rised lips (bared teeth), comissures (corners of mouth) going forward, lean of the body, and looking directly at the target.
In fact, if you take two dogs, one growling, and the other leaning slightly forward, lips drawn forward, and looking right at you, I really, honestly wouldn't be afraid of the growling dog if I didn't provoke it. However, with the dog that was silently leaning forward, staring straight at me, lips forward, I would IMMEDIATELY look away - and I mean IMMEDIATELY.
As a classic example, not long ago I saw two dogs standing around looking very relaxed, one was just sniffing the ground. All of the sudden, BAM: the two were going at each other like they were mortal enemies. I took some good bruises and cuts helping get the two apart, it was a serious fight. The others who saw it immediately said "That was so weird - one minute they were fine, the next they were fighting!" What I'd seen was that the dog sniffing the ground got a little too close to the second dog, so the second dog shot it a stern warning glance (VERY easy for the other dog to percieve), the first dog shot back a stern lip-purse (a CLEAR sign of aggressive intention to the to the other dog), and the fight was on. While that all took place in less than two seconds (maybe less than one second), it revealed that it wasn't really "out of the blue", and one dogs wasn't being picked on - both dogs had ample opportunity (from the dog's perspective) to back down, but neither wanted to. There wasn't any growling, just clean signs from both dogs that they wanted a fight, and so it happened. But, to the people who didn't know what to watch for, it was just "an instant fight".
I've seen this in every dog interaction I've watched - once you get used to reading the dogs' PRIMARY methods of communicating aggression, not only can you tell when something's really going to happen, it opens up an entirely new depth and richness in watching your dogs interract with other dogs and humans. It really does let you understand many times more what they're thinking and trying to get through to us thick-skulled primates that just don't seem to get what the dogs are trying to tell us!
As to whether it's right or wrong to teach your dog not to growl, that's up to you. In packs, puppies are taught by their mother, siblings, and other members that some behaviors are not acceptable. That's true of any social species, and there's nothing wrong with it. The right-vs-wrong aspect comes in to how you do the communicating. If you do the communicating in a manner which the dog readily understands and is benevolant in nature, there's nothing wrong. If you do things which YOU think the dog should understand (but he doesn't), or you're not benevolant in nature, then you're certainly not in the right.
steve