To be fair, Soarin DID give Rainbow Dash a chance to prove herself innocent. Granted, they had only speculation to go on for a case against Rainbow Dash, for all they know Stormy Flare could’ve indeed sent the letter and she forgot.

@Background Pony #9AAD  
I actually don’t even think Rainbow did.  
Well, maybe she did later, I forget (I do vaguely recall her saying she’d be kicked out forever) but if so it was just during the panic-attacks everyone in the Mane 6 gets (well, except for AJ and Spike, not counting episodes where they are made fun off by the writers (coughsomeponytowatchovermecough))  
Whenever she wasn’t freaking out, I’m pretty sure her ‘I need to figure this out!’ attitude was because she had to fly with the Wonderbolts (and/or did not want them to be disappointed in her)  
Which is more than enough motivation for her.

@aerion111  
Yeah, I thought it was pretty clear that what Soarin was saying was “You’re suspended until your name is cleared, and will be barred from the Wonderbolts if found guilty”, and Rainbow Dash took it as “You have one day to prove your innocence or else you’ll immediately be banned forever” because of her habit of overreacting and jumping to conclusions.

In their defense, she has motive, no alibi and a tendency to do this sort of thing (breaking into a hospital for a book, damaging the weather factory for her pet, etc.).

@Background Pony #A608  
Thank you!  
I totally agree, and I’m tired of everyone using this scene as an example of the wonderbolts being jerks.  
Yes, as far as I could tell, he said two things; ‘If you are found guilty, there’s no way I can let you join, ever’ and ‘I can’t let you fly with us while you’re still a suspect’  
Which is entirely reasonable; They’ve a reputation to maintain, it’s a large part of how they all earn a paycheck (people wouldn’t be as eager to go see a bunch of corrupt mercenaries fly as they would the glorious Wonderbolts, heroes of Equestria with a long and glorious history’

@FanOfMostEverything  
Well there’s a difference between not wanting to fly with a suspect pending investigation and banning someone after they are proven guilty.

@Background Pony #A608  
Yes, but moments earlier, he said this:

Taken with citing the bylaws, his intent was clear.

While I’m sure that’s how Rainbow felt at the time, Soarin’s words say otherwise: