Well.... I think it's a great diorama. It is full of tension and possibilities for the outcome. It forces you to assess the situation and read it for yourself - I love the muddy knife detail. Despite it being a tough subject matter, I find it no more offensive or challenging than disembowling, decapitation, torture etc.. etc.. It's certainly exacted a response.
With regards to the outcry.... for those who don't like it, why not censor yourselves guys? I would be saddened if work like this was to be censored and banned, or put into a separate little 'dirty secrets' category.
You are so very right on with your words. I will say that at this point in the argument, I'm not really sure what usefulness comparing violence and rape has anymore. I think instead of everyone focusing on "which is worse," we should be focusing on rape by itself and what it means, both as an awful, awful thing, and as the subject for a provoking art piece.
Also I should point out that asking someone to censor themselves is not going to make anything happen. If someone feels like they need to do censor art (or anything) themselves, it feels like work to them, and they would rather it just be censored already by someone else.
The impression I get is that people are offended by this work not just because of the content within itself, but that it brings light to the fact that this kind of content exists within the 40k universe. Perhaps because they use the 40k universe as a means of escapism (it is all fantasy after all), part of that escapism involves getting away from such cruel realities as rape, and now that aspect is gone to them.
To me, this diorama only enriches the 40k world, bringing in a new gritty element to an already gritty lore. To me it just makes the 40k universe more alive, deeper. Now we know that the 40k world is not just all unicorn farts and rainbow sprinkles (hah like it was like that anyway... 40k is already chock full of violence and adult themes). Do I like that rape exists in the 40k world? No, but I think it's more dangerous to pretend that it doesn't exist, even in this fantasy world.
I also thank the artist for depicting this scene so very tastefully, not just (absurdly) well-painted/converted, but with layers of thought and depth to it.