Him is put in quotation marks for emphasis, so it's significant, and Vegapunk says "please do not assume that the ones who strike me down are evil", which is plural, so the "him" could be referring to Imu and the "ones" as the Gorosei/Imu's underlings in general who Imu ordered to kill him, but it would be weird for Vegapunk to even give Saturn some benefit of the doubt and not assume he's evil when he objectively is lol.
Of course this is going by TCB, the translation could just be wrong and the official might provide more clarity.