Please stop complaining how Rainbow Dash "was turned into a jerk" in seasons two and three. For one thing, half of what you guys complain about is highly exaggerated and amounts to "Rainbow Dash was kind of snippy in this scene CHARACTER DERAILMENT." Second of all, there really isn't any of this "turning into a jerk in later seasons" thing going on. Do me a favor and rewatch some of the season one episodes. Say, for example, Dragonshy and Fall Weather Friends. You can't honestly say that RD isn't being a huge jerk in those. This isn't something that suddenly just happened. She has always been this way.
Third of all, you guys seem to have this idea in your head that RD was meant to be a perfect polite angel. Why? The fact that she's brash and egotistical is the basis of her entire character. It's what makes her interesting and fun. It's why she has a strong fanbase to begin with. She's always had an in-your-face aggressive personality. Being pushy, rude, and always wanting to be number one are her character flaws and they always have been.
Most of these "jerk moments" you guys complain about is her being frustrated and people get touchy when they're frustrated. Pretty much the rest of the cast is the same way - they yell at people when they're stressed out (almost every main character has done this at least once!), but for some reason it's Not Okay when Rainbow Dash does this. Rainbow Dash's character is a lesson that sometimes people aren't always nice, but that doesn't mean they're bad. Being mean and irrational sometimes doesn't make her a villain. Sometimes good people have bad moments. RD is still a loyal and hardworking pony who cares a lot about her friends. That hasn't changed. She hasn't suddenly turned into Gilda the Gryphon here. Just because she's a pony doesn't mean that she has to be perfectly sweet all the time.