Although it occurs indiscriminately all over the globe, humidity in its raw state is a tropical phenomenon. It prefers places with nearby bodies of water and can most often be observed in flagrante delicto, as it were, in the summer. In these regions and at that time of year it is often offered as proof that:
A) There is no god.
B) If there is, he really doesn't like us.
It is thus reviled because it does such nasty things. The walls of unairconditioned rooms in the tropics, in summer will start to bead with condensation which can give things a nasty case of mildew. If you didn't put a clothes pin on your big bag of potato chips, then they will get soggy. As destructive to life, limb and property as these are, they are not the worst humidity has to offer.
Humidity's primary demoralizing effect is caused by the fact that it impedes your sweat from doing its job. The human body requires your sweat to evaporate in order to remove kinetic energy and lower its temperature. But if the sweat cannot evaporate (because the air is replete with humidity) then it has no choice but to trickle down your leg under your pantaloons in an alarming manner. The upshot of this is that, due to trickling sweat, your socks will reach a state of humidity rivalling that of the air.
I for one, would advocate government regulation of humidity for the good of all citizens. Any humidity exceeding 70 percent should be brought into custody and prosecuted. Police would be issued barometers and any air that doesn't comply should be shot.