I sort of know.
Let's first agree on something: we each have the right to choose who to play with.
Now let's look at what the EN players are doing in the JP datacenter: JEDF and to hell with JP people.
Is it WRONG to say, we want to match up with English speaking people in the DF? Similarly, is it wrong for them to say they want to match up with Japanese speaking people?
There's really no solution to this. It's what comes with playing in a, well, for lack of a better way to put it, a "foreign" environment.