May I point out that Fi users can be liars, but it's not an inherent characteristic in Fi. Much like you explained, the need of self-preservation and self-protection can lead to lying, but not always. Fi also knows people's intentions well, therefore they might become good at lying. But in most cases, they don't like it, they just might not feel like they have a choice while interacting with the current environment. I've also lied, and tried to get the truth out when the chance presented itself, but when it doesn't, the truth stays hidden. My point is to not label all Fi users as liars and avoid Fi users because of that, even if on the outside they might seem like ones because of hidden internal processes.