This is my theory based on my observation on social media and this is the reason why Sheesh and BM got so much unecessary hate.
BP is the biggest girl group in the world and for sure they also have the biggest antis among all kpop group. with them being inactive and hiatus mood, the antis have nothing to do. so they went to Babymonster as Babymonster are BP junior and come from same company and their style of music are exactly the same. u can see the twitter most of account that criticize BM are the same account that also known as BP haters. sadly BM are still rookie so the amount of hateness that they received are too much considering their own fanbase is still new and growing.