Wow, I didn't know MONSTERS used the forum. You horrible monster.
Seriously though, I think the point intended by "A GM can't tell you how you feel" isn't that he can't tell you the feeling of a setting, but that he can't tell you what to think, what your opinion of it is. That becomes skewed when what he's telling you the result of a player's diplomacy - what you think about it IS how the speech makes you feel, typically.
You have me at a disadvantage. Not sure what you mean by monster.
But I agree, sort of--- opinions are all based on thoughts, but not all thoughts are opinions. SO -- I think that the GM shouldn't interfere with your opinions (or conclusions for that matter), but shooting you some emotional seeds is okay once in a while.
I think that a thought enters your mind. That thought may provoke an emotional response with little time to ponder. That emotional response is then further examined by our ability to reason, and then a conclusion is reached.
So my point is that I think it is okay for a GM to say: "The officer's passionate oratory gives you chills." or "The baliset's melody is soothing and you feel relaxed." or "The horrific countenance of the killer's face is unsettling."
I also think something like this is acceptable: The blaster bolt screeches by your head. A near miss. You feel a jolt of excitement when you realize that the shooter's blaster appears to have malfunctioned. He frantically works on it as you prepare to return fire.
Allow me to pose a question for all the talented GMs out there. How would you handle this situation: The PC wants to give a speech to a group of soldiers. These soldiers are all standing around the rest of the group. Simply put - the other PCs are nearby. The player is a bit shy, and just asks if he can roll his appropriate skill. He throws some dice. A resounding success! What would you, as the GM, say to the other PCs as you describe the scene?