Niji JP fans (especially those on 2ch) are having an increasing hate towards Niji EN. Some sentiment feels like "you are the black sheep of the Niji family". So anything could ignite this. Moreover, due to the devaluation of JP Yen and thus the huge amount of tourists, the hate towards foreigners in general is increasing in Japan.
Additionally, Meloco got a lot of hate from JP nijisisters. The sentiment is like, how dare you, a VTA skipper, talking to our glorious JP male livers in collabs?