Today I took 23mo DS in for a haircut as he's turning into the Dulux dog. He's had three haircuts previously, which we've got through with a combination of cheerfulness, distraction, cuddles, bribes, firm restraint etc. Whatever works, basically.
Today it was a guy I hadn't seen previously. I settled DS in the chair and explained that he was usually OK with scissors but tended to freak out with electric clippers.
His response: "Well, it's a case of start as you mean to go on. In my experience, whatever you do now, they'll be exactly the same when they're six or seven."
So I suggested we try scissors. As soon as he started, DS got quite agitated and tried to wriggle out of the chair. I picked him up before he could fall out (it was a good three feet to the ground) and gave him a hug.
Hairdresser immediately said "See, that's the worst mistake you could have made. You shouldn't have cuddled him because now he knows all he has to do is cry."
We tried various different things, all at his suggestion. Taking DS off to calm down, sitting him in an adult chair, sitting him in an adult chair with a cushion, with me next to him, with me sitting a distance away. Each time, DS freaked out and hairdresser just stood there and laughed till I intervened.
I asked if we could do it with DS sat on my lap or cuddling me, as this had worked in the past. He said no, because "Every time I've done that in the past, I've had to take two or three days off work because I've cut chunks out of my fingers." Even with clippers? Yes.
I suggested that it was more dangerous to try and cut a toddler's hair if the toddler was bucking and thrashing round, and he said "No no, there's no danger. I'm the only one here who can deal with the wild ones." Then we'd try something else, and he'd just stand back and do nothing while DS screamed. Eventually I'd pick DS up again (because this guy wasn't even TRYING to cut his hair), and then he would whinge about how it was all my fault for cuddling him at the start.
In the end I said to him: look, let's stop talking about what I've done wrong, and talk about how you actually plan to cut his hair, since you keep saying you can do it if only I "help".
At that point a woman started shouting from the back "You need to stop mollycoddling him! You have to be firm!"
Yeah, thanks. 
He then said he wanted me to keep settling him back in the chair every time he climbed out. Fine. So I started doing that. After about 5 goes, the hairdresser suddenly said "This isn't working is it? Can you get his dad to bring him in?"
FFS. So now, instead of a toddler who is mildly distrustful of haircuts, I have one who is (probably) downright phobic. And still no haircut.