What is he misunderstanding? There's nothing in the post mentioning copyright or suggesting the author thinks he has a legal case. He just thinks New Relic are being jerks.
Implied ownership claim is not a legal claim to copyright, and I don't see how the author alludes to it being so.
Aside from that - well, it was a pretty rude move, particularly in that they didn't bother to acknowledge him when he talked to them (albeit over twitter) before ranting about it.
I don't think there's a question that the conference can do this legally, but they're still being ass-hats by ignoring it (and getting his twitter account suspended).
Do you believe the marketing efforts that went into naming the Future Stack conference chose that name accidentally unaware of this person's domain and other online presence? If not, then I'm not sure collision is the correct word to use here.
I just don't think people have to abandon a cool name just because someone somewhere registered a domain or has a twitter handle with the same name.
Ideally you make up a new word for your new enterprise. But it ends up being harder than you think if you are trying to name something with an identifier that means something in a domain. Anyone that has to name a new product or company can attest to this.
In a world literally flooded by brands and names, name collision is not rudeness, it is almost inevitable.