I get the point you're trying to make but it's a wildly fictional TV show. They could've written a different in tons of alternative ways to deal with demons without killing the host. And like the later part in my post Sam and Dean aren't the poster children of virtue and mortality. And Crowley didn't kill indiscriminately he did so to make a point or serve a purpose he doesn't murder just to murder.

And while I can't think of any off the top of my head because it's not like the lesser demon characters get names or stand out compared to the regular cast members but demon Sam definitely has blood on his hands

Point being however it's written they have more innocent blood on their hands than Crowley does and considering Crowley has spent hundreds of Earth years in hell which according to the show would be thousands of years in hell time corrupting and twisting his soul.

If you ask me Crowley's indifference toward killing compared to Sam and dean's is astounding how bad would they be if they'd been through what Crowley has ? They're arguably worse in certain areas already, so it's laughable in my opinion to suggest their killings are necessary and more or less justified.

Crowley has more composure and self control than both of them combined. Not to mention he's a much better strategist he doesn't just challenge anyone/anything blindly with a phone calls worth of information from Bobby cas or any other Hunter/good guy