What does this mean? Is it bad?

It's part of a quest from a certain Faction. You receive that message regardless of if you're in the Faction or not, or if the quest has even been started.
There is no negative affect from killing the Netch before the quest begins, so no worry.

Questions like these should be in the Hints/Spoilers section of the forum.
It has to do with content in the game that pertains to quests/story/etc, and therefore not everyone wants to be spoiled by the answer.