Worse things have happened.
The Tribunal were anticipations of their Daedra. six and murder, plots and secrets, mystery and fate. Any Chimer would and should have done the same in their position. To not have embraced the Red Moment would have been to betray themselves. The consequences of each act must be accepted. Hence Vehk. Only his was true remorse, and through it he experienced both sides of this moment.
This is what you get for following Boethiah.
Of course worse things have happened, both in reality and in the dream but a brutal murder can hit on a more personal level than numbers and dates, especially a detailed depiction such as this. I doubt they're just desecrating a corpse, although that would probably be a graver crime in Resdayn. Does Nerevar accept this, as you put it,
‘any Chimer would and should have done the same
’? Or is this
‘foul murder
’ (I suspect the answer will probably be both)? Do the Chimer accept the betrayal of their lovers and friends as a part of their Daedra veneration? Is this foul murder through our human eyes but completely justifiable among the Chimer? In hindsight having a trio of god-kings looking out for you is great but I still don't know if it's worth even one life. Maybe I need to divorce myself from reality and slip into a more Chimeri morality. Although I don't want to end up trying to justify slavery!
Also, my mind can't help but wander to the ... practicalities of the event. Nasty stuff, but who can tell why elves do anything?