It's a commentary. Commentaries are
supposed to be one-sided.
The Guardian commentary appeals to emotion while making it clear where its sympathies lie. That is perfectly acceptable and proper for a commentary.
It's also quite relevant to the debate to bring emotion into it. You hinted at it when you asked whether "we're carrying out a lot more sorties than we did prior," but you only mentioned the military cost of it.
A key issue that the commentary highlights -- and perhaps the HN reactions to it as well -- is that we may be flying more drone sorties because the American populace is more comfortable with them.
It's a variant the old "smart bomb" argument from Desert Storm. If the U.S.'s only option was to carpet bomb Baghdad, then there probably would be more domestic opposition to the war and it may not even have happened. But the warmongers argued that we have smarter, more precise weaponry, which perhaps moderated opposition, leading to more horror and death.
Thus highlighting the actual horrors that drones inflict, and the widespread terror they instill in an entire population who live in constant fear they could be annihilated at any moment, is a very valid contribution to the debate.