I have had nothing to do with this guy but hear stories about how nice and helpful he is (from windsurfers).
That aside, IF any of the stories about him from kitesurfers are true he is
way out of line.Not saying Werner is right but an analogy:
Imagine kiters have always been at Lancelin in front of the main grassed area. No agro ever existed. In fact it was so good there and so popular a school and hire place started run by a guy called err lets say Warner

Skip forward 20 years and suddenly somebody invents jetskis - even better, lets say they tow a skier so they take up a bit more room.
Suddenly they use the same area at lancelin - even though they
could go 200m away downwind - and there are a number of incidents on the water.
Warner is upset that they are making it hard for his learners.
The kiters in general are upset about "their" area being stuffed up.
Only
some of the jetskiers are dangerous or a pain in the arse, but on some days the sheer volume of them on the water makes things a bit hard.
They could just go a bit further down the beach....
Would the kiters be up in arms, and would Warner the kite instructor / hire guy tend to go off?
As I said I am not endorsing his agro, just the door swings both ways guys.
peace.