I'll provide the copium and say that that guy's not so much a Nijifan as he is a "all corpos bad." They're the one who ran into flak
for the Silvervale piece a while back. I remember that after they ran into criticism for calling Hololive an idol thing he went back and edited it to add Nijisanji as well lol. They also got some flak from Nijifans for bitching about Kotoka saying "retard."
My guess is that in this case they saw Niji being shitty in regards to merch and decided to use that to rag on Hololive as well.