It's not subjective at all. I put the forum rule violated in the last post in the thread. Normally on a double post, I would close the most recent thread, but in this case they were posted simultaneously.
What you all don't see behind the curtain are the emails mods get from the "notify moderator" button. A member complains, I look to see what I can do and I do it.
There are some subjects that historically end up in the same bad place - like guns - and I'll do a "premptive strike" as Biscuit said. This saves me a lot of time.
To imply that moderators have an agenda in what posts get deleted and which threads get moderated more heavily than others is wrong and makes a thankless job even more so.