He „avenges“ Summer in this way not because it will help anything, if you give it a singular thought you can see that it is not something Summer would want done, it’s actually a cruel thing to do because breaking up with someone is not evil. Morty still punished him because he, like every other man, is expected to assume the role of patriarch, who has ownership over and the onus to protect the women in his family. Summers boyfriend infringed on Mortys on this which is why Morty choose a punishment for him, Morty wanted, not something that would be appropriate for the situation or in accordance with Summer.

I don’t think this is a „political post“ but what is and what isn’t is really up to the interpreter since everything is political. To me this is about familial relationships and media analysis, but I understand that for a lot of men this is a very emotionally loaded topic, so I understand the impulse to just remove it.