DMs are not always around and when they are, they can't always make every NPC do what that NPC should do in a particular situation. A city guard is not going to just stand by and watch as a huge fight breaks out just outside their gates. An NPC is not just going to stand by and watch if someone murders someone out in broad daylight in the middle of the city.
DO NOT post emotes which explain NPC actions of any kind.
In the same vein it's happened a few times recently that people have made posts directed towards NPCs that the NPCs would have probably reacted strongly too. Please don't do this, especially if the situation is a hostile one. If you're going to get hostile towards an NPC, or take an action that is likely to get a hostile reaction (such as you're a known good guy walking into the temple of Hel), please get a DM first.