First, he is not "clearly mistaken," only disagreeing with you. Second, merely because you agree with the OP, does not mean it is "marvellously written."
The OP is fraught with factual errors that I can only see as intentional so as to obfuscate the point. The shock collar is not inherently sexual. Any connotations to it being sexual reside on the side of the monitor not made up of pixels. Nothing makes this point more than the fact that you cannot shock her, then romance her, then shock her as the OP purports. To even begin to romance Vette, you must remove the collar. Yet, this spurrious line is included in the "marvellously written text" as a red herring, a means by which the OP can make it seem as though the two things are interconnected.
Nevermind the fact that you are in control of the choices your character makes. Nevermind the fact that Vette demands you treat her with a modicum of dignity for any romantic advances to find their mark. Nevermind that there exists an entire other line of conversation by which you can treat Vette as an equal, even a doted upon love interest, and even have her friends comment on how she has "softened" the big, bad Sith Warrior.
Further, of course the Empire is evil when viewed with our moral compass. That's what a moral compass is for, it provides direction by which we can navigate the intricacies of morality. Without a baseline, the notion of evil, good, or neutrality would be moot.
As to the assertion that the evil acts are hollow, and would be better served having a justification of sorts, there is a justification - the Sith world view as encapsulated by the Sith Code. To you, by means of your moral compass, this is hollow and lacks justification, but to the Sith this is their outlook, their moral center. See, that's how a moral compass works, because you and the OP are of a decidedly less than evil frame of mind the evil mentality seems hollow.
To pretend that any of these acts would be well received if only there were some greater justification for them is false. How would BioWare creating some sort of justification beyond that of "Evil Empire does Evil Things," allieviate the horror of genocide? Would a more detailed reasoning for said genocide be a salve for the OP? How? By my estimation, that creates a greater problem as you have now taken something the vast majority of us - even kids - take as evil and wrong at face value and created a means by which to justify the action. Now there would be something to get up in arms about...
Seriously, a diatribe to rail against the horrors of "sexual violence, slavery, and genocide" only to end with, essentially, "but, hey, give me better justification and it's all good."