Although beliefs can and do support each other, they cannot justify each other as at some point a belief must be anchored to reality in order for a belief structure to have any merit at all.
Take religious beliefs for instance. Examining a religious belief is like peeling an onion: after stripping layer after layer there is absolutely nothing at their core. Although some folks simply claim that they “know” that such beliefs are absolutely true – e.g., that a god exists – we can do little but take their word for it as they are unable to clarify what they mean by this assumption.
Beliefs in the existence of deities and other kinds of super-natural beings continue to show themselves to be a seemingly endless source of human tragedy. While they might in principle be no more than nonsensical and hence harmless beliefs, it is at the same time the sickly smell of centuries of savagery and senseless slaughter of thousands of people in the name of such beliefs – and primarily in the competition between such beliefs – when they become weaponized and a major cause of death and destruction on our world, from our distant past to the present moment.
One might claim that this kind of action has nothing to do with the religious beliefs themselves – and that they are misused when wielded as weapons of murder and destruction. No – it is precisely the unsubstantiated and irrational nature of these beliefs that allows them to be used in this manner. When you think you have the almighty creator on your side – all your actions are justified; you cannot be wrong!
Until we shake off the influence of these irrational beliefs, people will continue to be murdered for them.