I disagree. Suppose I do play the dragon to its strengths. I have him fly out of range of the players, and focus fire on the one player who is the biggest threat. So very quickly this one player is hurting bad, and near death, because the dragon focuses all its attacks on him. But in an attempt to have the dragon switch targets, one of the other players tries to intimidate the dragon to draw its fire, there by sparing their party member so he has time to find shelter and/or heal up.
Now if I were to play this dragon entirely to its strengths, it would laugh at the intimidate attempt, and simply finish the job. However, as a DM I recognize that part of what makes D&D fun, is the ability for the players to act and try and affect the outcome. If I just flat out deny them any opportunity to save their friend, I'm not doing a very good job as a DM in my opinion.
So there are two things I can do here. I can simply have the dragon change targets, which would be fudging a little, since I'm definitely having the dragon fall for something stupid. I'm not changing the outcome of a dice roll, but I would be having the dragon act in a way that is beneficial to the players and bad for the dragon. On the other hand, what I could also do is make a dice roll decide if it's a success. The player might have to succeed at an intimidate check first, for which I as a DM decide the DC. I could pull a number out of thin air, or I could base the DC on the intelligence score of the dragon, which makes a little more sense.
Here's the fun thing: which of those is fudging?
I don't think Iserith or Aaron or any of the strongly anti-fudging group would say that allowing the player a chance to change the dragon's behavior is fudging at all.
And if you set the DC based on something semi objective, say 8 or 10 + dragon's intelligence bonus, again I don't think anyone would raise an eyebrow.
But is it fudging to simply have it work, no die roll? (Again, guessing Iserith would say no, unequivocally)
Is it fudging to set the DC fairly low, say, 10?
What if you set the DC to "X+the player's bonus to intimidate checks" with X being 5 or 10 or 15 or whatever you want the roll to have to be? Fudging or no?
What if you don't set a DC at all, and just have them roll and then estimate gradual success based on how good of a roll it was? Fudging?
Or is it only fudging if, after you set a DC and have them roll, you secretly change the DC to force success/failure?
What if you set a DC, and then as they roll the player also shouts, in character, some additional insult beyond the ones that prompted the roll? Something absolutely perfect and intimidating? Do you change the DC now? Declare auto success? They already rolled. You can't unsee it. Is that fudging?
I have my own opinions about all of these, but I don't think they're all obvious answers. Curious what people think.