It wasn't supposed to be a game where you kill cops, that was just the first enemy I finished and I didn't have time to make more. I was going for a theme of prohibition-era gangsters, so was planning on focusing more on inter-gang violence, but I ran out of time.
I do realize this sounds like an excuse however. I had considered that this game might be somewhat problematic, but I will make sure to put more thought in in the future.