Rarity just told him to bend over, but Spike (and his poor, poor anus) had had enough.

@Background Pony #27D3  
He took a huge level in badass standing up against his aggressive dragon peers too. Turns out he doesn’t like killing defenseless creatures for initiation rites.  

If placed in the same situation, I don’t think I could have told the truth. I may know that telling the truth would be the right thing to do, but I’d probably try saying it, but being quietly due to being nervous. Then the other would not be able to hear it, and if they acted negatively enough, I’d say nevermind and probably never bring it up again.
 
So that is the major reason why I find this moment to be so interesting.

It takes a lot of cojones to stand up to your enemies.  
But it takes much more to stand up to your friends

And even though no pony noticed, Spike took a level in Bad-Ass that day…

@Revan0123
 
Oooh, colour me interested.

Spike: No.  
Rarity [Possessed]: What did you say?  
Spike: I said no.  
Rarity [Possessed]: What is the meaning of this negative?  
Spike: It means no.  
Rarity [Possessed]: But your friends will die!  
Spike: No! Because this is what I’m going to do. I’m going to rescue them. I’m going to save my friends from the middle of your rampage and then I’m going to save you, and then, just to finish off, I’m going to wipe every last stinking bit of Dark Magic out of your body!  
Rarity [Possessed]: But you’ve got no weapons, no defences and no plan!  
Spike: Yeah. And doesn’t that scare you to death?
 
(Sorry guys, had to do it when he said that)

@FanOfMostEverything  
Makes me want to add an ‘inner conflict’ tag.

@gittonsxv  
Learned to say no to Rarity, specifically.  
Possibly the most difficult ‘no’ he’s ever uttered.

and thus, spike learned to say no.
 
god that sounds bad out of context…