Oh, you must be an alien. My species, humanity, has been displaying the corpses of criminals for the entirity of its existence and continues to create paintings, songs and movies about it. The question is more "Is it art, or is it porn?", followed by " Is porn art?". Find me a catholic church which doesn't have a cast crucifix. That the ants were in the 'mold' feels like an implementation detail. They were scheduled for death. Weather the aluminium was poured before or after the extermination feels like an implementation detail. But do I want one? Fuck, no. It was interesting for science, but once was enough.
"Hey, look at those ants on that blue planet. Are you ready to fire the Death Star?" "Armed and ready, planet has gone molten. Awesome, get the contracts ready, I got dibs on the cast of the NYC subway, I heard that those ants really loved those tunnels, man, it's gonna look awesome in my gazeebo."
Bad taste yes, but bad taste is subjective. Morality (should be) objective, so it's one thing to say "I don't like this" (I don't like it either), and another thing to say "nobody should like this".
Morality isn't black and white. It's somewhat bad to be killing ants but let's not say it's on the same level as killing sentient life. It's just a rather shitty thing to do.
Considering the very thing that is the object of beauty, it seems perverse to have destroyed it and its forebearers in entirety to produce it. Something akin to a buffoon's take on art.