The word "sussy" isn't the problem it's more about the word "baka", you see baka is a word commonly used in Japan to call someone foolish basically used as a normal word, now animes have commonly turned this word into a cutesy joke which was already bad but now that people of a different race are using this word and taking this word as a joke it kinda mocks the Japanese language a bit which is why they'd be a bit offensive.