I agree with this. I am not afraid of letting the characters win, but I do try to be fair. And, if the characters happen to get lucky in combat, or take out my main opponent in one shot-so what. I don't care, and I will celebrate with them. I try to be completely impartial.
I follow the advice that Eric Wujick had told me during a seminar that he had. In his game (and in mine), there are only two ways for a character to get killed. They are 1) through character actions (and I do try to provide hints when there is a potentially lethal situation), or 2) through combat.
If, in a fantasy setting, a character finds a pistol, puts the barrel in his mouth, and pulls the trigger, thinking that this is some kind of magic item that will improve his character, and the player is playing the character IN CHARACTER-well, the pistol will happen to be unloaded. The PLAYER may know what a pistol is, but the CHARACTER would not. That is an example that Eric gave.
Combat is another thing. Runequest is a dangerous game, and smart players will avoid combat.