I don't have any problem with the graphic and descriptive story about murders and animal killings, it's very common for films to be made around these subjects.
Here are the things I disliked about it:
I absolutely disliked the execution of the documentary. It seemed lazy to me. The story is of the year 2010-2011 when the cat video is uploaded and the Facebook group is created.
To show that old Facebook group, they just screen-recorded a "made-up" group by the same name on (new) Facebook. They could've at least animated it in the old Facebook/internet style. Just the screen recordings looked so lazy. Same with the google maps interface. No transitions, framing, or anything was done when switching between the internet and talking heads.
The makers gave a lot of unnecessary details to the story which just made it slower and time-wasting. One of the two "self-proclaimed" saviours, John Green was just annoying, he'd describe the most unnecessary details in a very irritating way, and for some reason, the filmmakers decided to leave those time-wasting slow moments in the final cut.