Concerning G-d and the Holocaust:
It seems to me that is you are going to blame G-d for whatever bad that happened, then you are implying that G-d runs the world. At that rate, to be consistent in thought, then a person should have to praise Hashem for all the good in one’s life (from the simplest to the most complex). If one can really be that cognizant of Hashem, then the question won’t really bother you.
On the other hand, if one believes that the good that happens to mankind is a product of our own doing, then (in being consistent) one should see the Holocaust as a product of man’s doing. In this case the questioning of G-d is useless.
In short, the question comes up by people that are either inconsistent and/or ingrates.