The NPC doesn't have an "Intimidate check" simply because it is trying to intimidate a character. A Charisma (Intimidation) check is called for only when the outcome of the attempted action is uncertain.
there is uncertainty no one knows how well in game the NPC does until he tries... you can describe and say all you want all that does is show how good or bad a orator you are (based on what you say you are quite skilled) how ever that is just you telling a story. Your NPC can be good or bad get lucky or unlucky, but your way doesn't take that into account at all. You say no check needed, I say "Yes there is, your CHARACTER (Pc or Npc) is trying an action, roll to see how well they do"
In the case of an NPC trying to intimidate a PC, the outcome of the attempted action is not uncertain because the player whatever the player does in response is the outcome.
except it is your out of game skill to tell the story and the players out of game skill of interpreting what you say or mean, and at no point is it refrencing the game world. You have ripped 1 whole pillar out of the game and just said "My way is better"
Thus there is no need for an "Intimidate check." So I can't be hiding one.
skill checks show how well or bad someone performs an action... the fact that I can describe my awesome jump, and/or do an awesome jump in the real world won't help my str 7 untrained in athletics and at disadvantage due to weight/encumbrance character jumping a 7ft pit. You can describe the intimidation all you want, but like jumping if you don't roll it in no way is tied to the character in the game it is mearly you out of game saying something...
it would be like me grabing a nerf sword and throwing you one and saying "Ok now lets see if you hit my hobgoblin?" see my hobgoblin has an AC, you have an attack mod... or in this case your monster has a skill use it instead of your skill in telling stories...
Mechanics in an RPG cannot prevent you from trying things.
sure they can... the mechanics say my 2nd level fighter can't cast fireball... nothing I do, no matter how well I roleplay the exact semetic componenets will let me...
well it's a subtype of game, just not board....
The DM/GM may say that you succeed or fail based on a mechanical consideration, but that is a different story.
no it's you word lawyering...
In your position, I would have tried to break that spell by resisting and let the GM tell me what happens.
bull... in a game where you know that once an effect happens there is no way to undo it you would attempt to undo it knowing that it wont work in the hopes of working around the 'don't ask questions' rule... why not just skip the stupid middle parts and just explain what happened and let the PC ask questions...
At the very least, I would have tried to determine if I was indeed under a spell rather than make what was later proven to be a bad assumption.
there is no way to determain if you are charmed in game... you can (if you have a resnable DM that lets you just directly ask quastions) ask if you are under a charm effect out of game..
Edit: To be clear, I don't condone how the GM handled that situation. But to say that what happened was due to a policy of "no questions" dismisses other options you had available to you to affect the outcome.
bull again you want to dance around and pretend there are all these options instead of just letting the PC ask you to clearfiy...same way he did.