1. He regularly disarms Rick's neutrino bombs. The first time he did it it was completely on the fly, no prior experience. Yet, he did it.
2. He has a knack for learning alien languages... as for the tree people in the battery dimension, it was obviously done without any sort of translator or support. (And he took over as their leader)
3. He's quick on his feet and can think his way out in a stressful situation, figuring out things that Rick can't and coming up with innovative solutions.
4. He figured out how to use a portal gun.
5. He can figure out how machines he's never seen nor used before work, and employ them successfully.
6. Beat Rick (smartest man in the universe?) in a board game.
7. Can manipulate said "smartest man in the universe", if he so chooses.
8. Became a successful stock broker. Out of the blue. Just did it.
9. Run. Whole. Freaking. Civilizations (and also toppled them as Marta)
10. Pitches good ideas that Rick typically ignores
11. When suddenly becomes motivated to try, he is good at math
12. His ideas were good enough that he would have gotten a deal for a movie production...!
13. His default intelligence is maxed out.
...At this point, it's only a matter of time before he starts making his own inventions, Eyepatch-Morty-style.
The only reason we've been thinking that Morty is stupid is that Rick has been calling him stupid repeatedly.
Sure, Morty does plenty of dumb stuff, but so does Rick. Rick has the emotional intelligence of a four year old and throws tantrums of cosmic proportions whenever slighted (vat of acid? submit to the selfie?), while often going ahead with complicated, innovative ideas... that in reality solve nothing and are a waste of time (Pickle Rick?? Leg Rick?? Cloning his own daughter? The dumb time-loop in his own dimension? Replacing himself with a robot? Creating a robot ghost to scary Mr Poopybutthole instead of just telling him to leave??) Not to mention his many incredibly lame jokes.
Everyone does dumb stuff occasionally!!! No one is an impeccable genius of non-stop moments of brightness!! (even Eyepatch Morty, the most cautious character, the character who has made basically NO MISTAKES up to now, sounds dumb a couple of times: "I'm gonna do the thing I wanna do, with the curve thing" and "My biggest fear is other people being afraid. Of fear. Itself." lol).
If Rick hadn't been calling Morty a freaking idiot with every breath available, we wouldn't be thinking "oh look haha the moron became a stock broker, what a joke, must be some sort of fluke"; we would be thinking "what an incredibly gifted kid".
We would attribute Morty's many mistakes to lack of experience, to lack of wisdom, to youth, to enthusiasm, to idealism, to teenager hormones, to acting hastily.
We would wish to see him eventually mature, apply his time and effort to worthwhile endeavors instead (mainly) of inane teenage stuff. We would wish to see him do well in school, we would wish to see him reach his full potential and succeed in great things.
Only Rick keeps pounding our heads with how stupid Morty is, and all of Morty's successes are never mentioned again, but getting lost to oblivion in comparison to Rick's (who has 60+ years more experience) genius.
WE VIEWERS ARE BEING UNWITTINGLY MANIPULATED THE EXACT SAME WAY MORTY IS.
