This is why the shout was brought up. Seems pretty clear why people have issues with that type of behavior.
However, I'll chime in with a related annoyance: people who PK others going for 200 and then shout about how they are preventing that person from getting to 200/etc to showboat it around. I will acknowledge that yes, in this example, it was perfectly acceptable as far as where and why the PK happened. However, the shouting of deliberately trying to prevent someone from getting 200? Come on now. Poor form. That's just asking for people to start preventing the offender from getting to 200 and treating that individual worse. It, contextually, ends up driving some of those attitudes/tensions that are frustrating for anyone to have to deal with.