Updated: Dec 26, 2021
***MAJOR SPOILERS AHEAD***
After Peter Parker and Doctor Strange messed with the multiverse, they had a chance to fix everything by sending the villains back to their respective universes. But, there was a twist. The bad guys were being sent to die. Doctor Strange was okay with it but Peter was not.
Why Doctor Strange was right
Doctor Strange knows that it is risky to mess with the timeline. Therefore, he respects the villain's fates. Even if, there are debates over who decides someone's destiny or not (Higher power or oneself), we can all agree that actions have consequences and that the end of every villain is the result of their works.
One of the saddest parts of the movie is when Peter realizes that he officially lost everything, including his family, friends, and academic life. He suffered loss, survived a traumatic fight, endured financial insecurity, and ended up alone. Mentally and physically, it is no doubt that Peter is struggling which means that he can't give his own universe the best of himself. Despite the heroic tendencies, Spider-man has to prioritize his loved ones and the safety of his universe.
3- Hero complex
When we think of it, each multiverse has its own Spider-man who is responsible to keep the villains away. Therefore, it was not Peter #1's responsibility to fix them or save people from other universes. Earlier in the movie, MJ had to urge Peter to inform them before he tries to help them get into MIT and it was right after he and Dr. Strange tried the spell.
Why Peter was right
1- There is a difference between a villain and a victim.
It can't be questioned that Green Goblin, Doc Ock, Electro, Lizard, and Sandman are bad guys. However, it's not exactly the same for Norman Osborn, Doctor Otto Octavius, Maxwell Dillon, Doctor Curt Connors, and Flint Marko. They are flawed human beings but they are either infected or possessed by another entity. Only a Spider-man could see below the surface.
2- Everyone deserves a second chance
This saying is as old as time but couldn't be more relevant when it comes to the villains. As shown above, it was not entirely their choice to turn evil but it was sometimes the consequence of their ambitions and carelessness. Regardless, they have caused many harms and by giving them a second chance, all three Spider-men thought it was worth all the risks to cure them because the purpose of a hero is not just the fight, it is the fight to restore.
3- With great power comes great responsibility
Unlike the other Peters, Peter #1 was part of the Avengers, had a more developed suit, and had access to the multiverse, through Dr. Strange. He was the most powerful Spider-man ergo the one who owed the most to the multiverse. Therefore, curing all the villains was part of his responsibility.
Who was right then?
I'll leave it up to each and every one of you to decide.