Q: Should bitcoin be backed by something like bullion? Gold, Silver, Oil, Platinum?
A: No. Bitcoin is backed by math, miners, and the protocol.
Some problems with having a backing: Having something “back” bitcoin means that there has to be someone who is holding the something that is backing bitcoin. The person who is holding the backing has to have some kind of gain (e.g. pay to do their job), and this puts that person doing the holding at risk of having the item backing bitcoin stolen, “seized” or confiscated.
In short some type of “backing” creates the very problem that bitcoin solves, having a central authority who is corruptible. Bitcoin is decentralized, this centralizes bitcoin.