I've been reading the various printed works for Touhou, and they seem to give conflicting view on the relationship between humans and youkai in Gensokyo.

"Wild and Horned Hermit" more or less portrays youkai as fairly harmless (even Reimu says that they behave more like eccentric humans), but this is clearly in contrast to "Perfect Memento in Strict Sense" where Akyuu warns people to be careful of youkai and gives them threat and human friendship ratings. "Forbidden Scrollery" actually portrays them as threats to the human village, with Reimu taking a fairly proactive approach in investigating any weird occurrences in the village and even exterminating a youkai that hasn't harmed any humans.

Granted, given both the (exterminated) youkai's surprised reaction to Reimu's actions and Kosuzu's dismissal of Akyuu's warnings about becoming a youkai, it seems that there are some discrepancies in how the humans in the village view youkai.