I think it's a pity that people can't see past him being "combative and dogmatic". I don't agree that it takes away from the core message of his work at all.
A lot of really smart people are cantankerous, and often they can afford to be.
The only time I've met Zed I found him to be a perfectly pleasant and non-cantankerous person.
My understanding of his approach to teaching is that it's based getting people to do things that bring results and then getting them to understand why after - which I think is a perfectly sensible one for beginners
It is very good. There's an educational philosophy around this that state that people who are new need to know "why should I care" first, then "how do I do it" next, followed by "ok, why does it work that way?" last.
When you're cooking, you follow a recipe. When you are learning to be a cook, you graduate to figuring out why you do it the way the recipe did.
And when you get really good, you start saying things like "Well, I wouldn't teach people to cook THAT way! That's wrong!"
A lot of really smart people are cantankerous, and often they can afford to be.