By my experience, i'd say that some people target you to ruin your day.

[Mao]

1. Wild and Nomads are here to kill humans. That's their only purpose. They may chose to use you, they may chose to simply waste you but the final goal is to kill all humans. You obviously don't know this simple piece of lore.
2. The first thing you told them was "HELLO PERSON WHO SWALLOWED A WORM". Like you just know they're aliens. That's called metagaming and usually players will engage you if they see you can't play your role according to your ID.
3. The fact that you want to play with NPCs and don't harm other players doesn't make you invisible to other players. You're playing on a live server.
4. Piracy in capital systems is bad. They're supposed to be the best defended systems of a house. This time it was D9, next time it will be LN, LPI, LSF or some merc. Unless you're good at PvP or you come with a lot of buddies, you will end up as a blue message.

Now, some free advice to you: Familiarize with the way you should interact with Nomads/Wild. Angels should be able to help you there. Read the lore, the politics and the history of Sirius. That will give you a good picture. Do cargo piracy (against NPC or players) outside house systems or as far as possible from the lawful entities. Be sure to always have an escape plan.

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