Sometimes fear is rational. To be scared of a spider or snake when its leaping for you is rational. To be scared by a balloon is irrational. Fear of a balloon is an irrational fear. when you know logically the balloon wont harm you. Being scared of a harmless house spider, while irrational, is linked to a rational fear of spiders. Human emotion is complex.
Im not really clear on your intent with this post because you seem to say opposing things.
RE: Irrational fear doesn't exist!