Fi creates ethics internally, and it's not just by "being overwhelmed with feelings" it's also by learning, contemplation, and reflection - it's actually a logical function in it's own right - like Ti - except it's ethical rather than rational. Fi can give one a philosophical bent about human relationships, etc. I am of the opinion that people whose Fi is completely WTF selfish actually have underdeveloped Fi, like seemingly-heartless young ENFPs or ESFPs are usually in Ne/Te or Se/Te loops without appropriate levels of Fi.
It also does tend to revolve around universal feelings of feeling empathy for the pain of other beings, and I think those ethics are more feeling-derived. Fi generally realizes that what is right for them isn't right for everyone, but I think even more so combined with Ne rather than Se, it can give one this holistic world view that there is no "right" or "wrong" culture or way of being, yet there are common threads (like respect for life) which connect everyone, for example.
On the other hand, IxFPs with no Te can look really irrational and be frustrating, just like TJs with no Fi can look like borderline sociopaths.