Even if all that was true, that doesn't make bargaining with the in-universe equivalent of the Devil himself to wish it out of existence ok. I mean, sure, divorce sucks, but it'd have been a better, simpler solution, especially after the harrowing of Civil War and Back in Black, for Peter and Mary Jane to split up because Peter felt like all he'd brought into MJ's life was pain and misery and death. But trading their marriage to Mephisto as the "price" of saving Peter's aunt May from the consequences of Peter's own decision to trust Tony Stark enough to publicly unmask as Spider-Man was a betrayal of the very core of Spider-Man --- which wasn't being a swinging single twentysomething bachelor, but someone who swore to never shirk the great responsibility that came with his great power after his negligence and apathy towards a seemingly common thief cost the life of his uncle Ben. "Oh, but it's ok because now Spidey's not being held down by the millstone of marriage anymore"? Very well, then.