This part has been proven to be wrong as now almost any idiot in Star Wars can switch on the lightsaber.

It's not. With lightsaber you can still block the counterattack if the trick didn't work as expected :D

That's the great answer actually. Maybe you should put some quotes in your response from that wiki article.

From the movies and other sources (like games) it looks like the speed of turning on the blade hugely depends on owners will. Sometimes it is slow (kinda dramatic), and sometimes lightning fast.

Insightful. Thank you :) But imagine that you own the saber that cannot be blocked. Does the opponent has any chance against it, whether he aims for the weapon or your head?

Well... consider the opposite then. Let's say you attack and your opponent throws his hand with the lightsaber forward hoping to block your attack. And rather then actually hitting his lightsaber you turn it off passing the block and turn it on again. There you have it - dead opponent.