The thing with topics like these is that it's very easy for us as consumers to say "just do it, sod the consequences", but the reality is that any PR blowout from something like this would incur serious financial hardships on Bethesda. While I'd like to think that the world is ready and willing to take responsibility for mature content in video games the fact of the matter is that it's not. It seems that the interactive nature of videogames means that subjects that are acceptable in books and cinema are deemed unacceptable in games.
If a game is rated 18+ it doesn't make a difference to who actually gets to play it. I've seen parents buy games like GTA for their 6 year old children because "games are toys", then they blame Rockstar for introducing their kids to [censored] and murder. These are the same people who would never let their kids watch an 18+ rated movie, or read an erotic novel.
It's no wonder developers skirt these things when the majority of people have proven they cannot be responsible with the content and who accesses it. Rockstar can get away with it because it's what they're known for, unfortunately Bethesda is not, and is therefore not equipped to correctly handle the backlash, that and it's not so obviously satirical in a Fallout game.