Honestly, I really wanted to like Discord a lot and to regard him as one of my favorite MLP characters, I really did. But the way the writers portrayed him and made him do stupid actions and decisions all the time (like you said yourself) has really dimmed my perception of him overall. I really dig his relationship with Fluttershy, Big Mac, and Spike, but other than that he's been unnecessarily rude to the other characters. I wouldn't mind if it were sometimes, since being snarky seems to be part of his personality, but doing it all the time is just overkill.
Well, I can't deny that Discord spends much of his time being a jerk. No beating around the bush there! 
I actually used to dislike him quite a bit, but after Season 4 he somehow began growing on me. I realize he's not everyone's cup of tea, though. The way his personality demands attention both from the other characters and from the viewer every time he shows up probably contributes to how fans are divided between loving and hating him...not a lot of neutral ground. I was disappointed that certain episodes involving him (What About Discord, Matter of Principals, the show finale) did not fit with the character arc they'd been giving him earlier at all. I wish the fan theory that he'd actually been trying to trick the villains into reforming when he released them would've been correct--that would've been far, far better development for him.
Did I mention that when director Jim Miller was interviewed on the season finale, he said that having Discord be Grogar made sense considering Discord's weird logic, then went on to say Discord was his favorite character?? Just--gahh--what--WHY would you give your favorite character such a poor ending at the finale of the show? How could you twist his development for the sake of some "big reveal" that, no matter what you may have thought, DOESN'T make sense?? You betrayed me and the rest of your fellow Discord fans, man!!
Now that you mention this fan theory, I agree. And yet, we end up with Discord screwing up everything once again, and he and the others had to
rely on the Mane Six to set things right
again. Yes, we as humans are bound to make mistakes once in awhile, but it seems like something Discord somehow commits on a daily basis. I do admit, Discord utilizing his cunning style to trick the villains into freeing Starlight Glimmer was pretty cool on his part, but does it really make up for the mistake he had done earlier? The Mane Six believes so, but as for me, I'm not so sure.
Also, hasn't Discord essentially thrown "temper tantrums" in the past because the other characters leave him out on certain things? Like when he doesn't get to be the head principal of Twlight's School when she was out of town? I know how he feels, but he should realize that the world doesn't revolve around him and there's a reason Twilight Sparkle chose Starlight Glimmer over him. And he only stopped after Starlight said sorry to
him. Talk about her appeasing to the aggressor of all things, the one that turned into a ghost and terrorized the school just because he was rejected a position in Twilight's school. Yikes.
