I saw this same excuse for Sins Past. Having a one-night stand with Norman Osborne and having his children humanized Gwen Stacy and made her more realistic.
Marvel must have a really dismal view of humanity. My theory is that these stories are written by Silver Age J. John Jameson. Having characters who are better people than them makes them feel that their lives are meaningless, so they make sure the "good" characters are worse people than us.
I've never gotten so drunk that I slept with my roommate and couldn't remember whether I had sex with her or not, and I found it easier to relate to a Peter Parker who hadn't done that, either.