I would not turn down the job because of content. But I wouldn't take the job if I wasn't sure if they weren't "ethical". The porn industry has a dubious reputation. I would have to be sure they wouldn't be involved in spamming, malware, nasty javascript, annoying popups, etc, etc. And on the non-technical aspect, I would to be made sure they aren't involved in anyway in forcing models to do what they do not want to do. I have turned down jobs because of that reason (not from the porn industry, but from the industry that's pushing ringtones and expensive SMS-based games)

But I would not balk at the content.

Besides, I've worked for banks. That got to be worse than porn.