Talk:Grimm/@comment-29933641-20170215162955/@comment-4010415-20170215213244

Yes, they're aware that negative emotion attracts Grimm. Oobleck outright stated that in Search and Destroy.

Oobleck: There are a number of reasons why Grimm will congregate in this particular area, the most likely of which will be their attraction to negativity: sadness, envy, loneliness, hatred. All qualities that are likely held by our hidden group harboring ill intent.

I feel like they also said it somewhere else in the show, other than WoR: Grimm, and I remembered just a moment ago, but I've suddenly forgotten.