Do I approve of nudity in a presentation? No. But at the same time, even if I found it offensive, I wouldn't turn it into a huge argument and the focal point of a rant against a community.
I'm really, really in the minority with this statement, but I find it very easy to deal with intolerant people. I have friends who are almost certainly racist. A lot of the people I know are casually homophobic. I think that's sickening, but I don't turn that into a rallying point of a campaign. The attitude that I was taught as a kid was that the best way to change things is to lead by example.
Now, being upset over using nude women to draw attention, that makes sense. Voicing displeasure makes sense. But there's a line between that and turning that issue into one that directly attacks the community. When you're part of a community about coding, you'd best be focused on the code. If you don't like DHH, you ignore him. If you don't like Obie Fernandez, you ignore him. The language is what matters, and it's a large enough language that if you know what you're doing, you can find people who are willing to help.
Now, look at the attitude of the Rails community towards beginners: they are incredibly kind and cool and open about it all. (This extends to what parts of the Ruby community I've interacted with.) If you don't know a thing about programming, they'll help you, and they usually come across not as nerds but as socially normal people. I don't know if they really are, but their leaders certainly are: they have their priorities straight. I've never been party to a group of programmers that seemed as normal as the Ruby bunch.
So when DHH applauds the presentation, the message he's giving isn't "RoR approves of this." He's just saying this as a leader. He's saying this as DHH, a rude dude who loves to be crude. The fact that he's the leader is entirely apart from the fact that he's saying this. That's why he's so interesting to read. That's why 37signals is such a good blog. It doesn't matter that they're rich and successful and in charge of stuff: they're a good blog because they write good posts, and all that other stuff is an aside. Meanwhile, in the rest of the programming world people are all-too-quick to judge a person as a single, solid entity. Steve Jobs is evil because iTunes has DRM. Bill Gates is stupid because Windows is ugly. Jason Fried is a jackass who never does work because other people waste their time reading SvN archives. Ruby on Rails is bad because their developers are immature. It's the same approach of solidarity that leads nerds to decide all jocks are stupid, all different people are meaningless, and anything that looks nice can't be nice because it's coming from non-nerds.
I would say, though, while you are deliberately choosing not to ostracize the Rails community, they are deliberately ostracizing people who don't like porn, or at least people who don't like porn at their tech conferences.
Is this any better than a nerd insulting a cheerleader for asking an unsophisticated programming question? Implicitly, they are saying if you aren't cool or hip enough to not be offended by a pornographic presentation, stay away from our conferences.
A little elitist, no?
It also depends on what you mean by "insulting." Frankly, if a cute girl asks me to program, then I will almost certainly tease her as I help out. I think the porn thing was an attempt at tease that ended up being a bit too insulting. There's definitely a line, but usually if you cross that line people will understand so long as you do.