I'm guessing its probably related to the fact that BG1 and BG2 are T-rated, BG3 is both M-rated (in part for sex) and inclusive in a way that, well, more than one review or article suggested it might be something like “the queerest video game of all time”.

To be clear, I'm not criticizing, I just am not surprised that a certain segment of the BG1/BG2 fanbase is unhappy.