Introduced and used properly, I don't think they detrimental to the dogs. I have seen people hold them way far away from the dog so it's like the poor thing is in a wind tunnel or not paying attention to where it's blowing on their face and ears. I always keep it close to the skin to control where the air is flowing. I never blast them in the face either. Again I keep it close to the skin, keeping the air flow away from the eyes and nose and I always hold the ears closed.
When I hear force free grooming, I think of it in the ways of handling the dog, not the dryer. That doesn't mean it's not about dryers. I just never looked at it that way. :)
There are dryers on the market that are adjustable speed with a dial. You can keep it down low and with no adaptor on the hose for a very light flow of air, or turn it up and put an end on for more power.
If you don't go after what you want, you'll never have it. If you don't ask, the answer is always no. If you don't step forward, you're always in the same place.