Sorry, I haven't been able to find a definition. I found that some other people have thought of this too, though. For example:
But when there are only two flawed parties to choose from—one consisting of a loose coalition of minorities and the other a self-homogenizing group—there’s really no room for a third, more honest option for those of us who fall somewhere in between. "What makes someone a ‘person of color’ or ‘white’ in America?" by Daniel Rivero, fusion.net
This phenomenon [trend of push-and-pull migration away from rural areas] isn’t unique to Galesburg. It happens in places like Quincy, Pekin, Elmhurst. The list goes on of these fuck-up towns. They become self-homogenizing. Then they run themselves into the ground because of their lack of diversity. "The Opposite of Suicide II" by Kyle Mustain, writingdisorder.com
Let's try it out in your sentence.
The clique tends to have a self-homogenizing culture: once someone suggests an idea, the whole group clings to it.