Traditionally, Brazilian Jiu Jitsu is done both in a gi AND not in a gi.
I don't even think there's such as thing as a "gi only" school --Is anyone here from a BJJ school that doesn't offer ANY no gi? I always train no gi when I travel and I've never run into a BJJ school that didn't have offer a no gi class.
Truthfully, the whole "gi" vs "no gi" rivalry only goes one way.
Most "traditional" BJJ players usually train at least some no gi. Most like it or at least see the value of it. I don't really hear many traditional BJJ people say they "hate" no gi. I've heard it, but very rarely.
But people from no gi schools, on the other hand, act more like vegans; They don't just not eat meat, they HATE meat. They commonly say things like they "hate" the gi and refuse to ever wear one. They are actually against the gi. That's more the norm there.
As mentioned above, the great thing about the traditional approach to BJJ is you can train with ANYONE who grapples; gi, no-gi, whatever. Problem with no gi purists is they will only train with other no gi people --and that's probably one of the major contributing factors as to why so-called "gi players" do so well in no gi competition.
It's kind of ironic that the "traditional" approach to BJJ actually seems to be the more open-minded one.