*vibrating with excitement* oh boy is there a lot to unpack here
First off, where each of these performers are from. Asuka is famously from the Kansai region and Io is from the Kanto region. Osaka v. Tokyo have New York v. Texas levels of beef.
Second, ‘baka’ is a mild insult in Kanto-ben (Tokyo-dialect) Japanese, but a MUCH heavier insult coming from the Osaka native. “Dummy” vs “Moron” is probably a fair comparison. Although Asuka’s almost feral levels of how heavy her accent goes probably elevate this to “DUMBASS”.
Finally, the fact that Io’s final retort is subtitled as ビッチ! instead of “Bitch!” is obviously funny for the reversal, but 'bi-t(softened version of the usual 'tsu’)-chi’ has a VERY DIFFERENT MEANING in modern Japanese.
Io didn’t just call Asuka a bitch. She called her a /slut/.
ETA: And, of course, Corey 'I love other people’s problems’ Graves on the side, with “I know what baka means! :D ” is just the cherry on top.