Look, I'm pro nuclear power, but the "already dangerous material" is not naturally more dangerous than spent fuel. We concentrate and enrich natural radioactive materials to turn them into nuclear fuel, and in that process make them incredibly dangerous. So yes, nuclear byproducts are less dangerous than e.g. freshly-enriched Uranium, but not than raw ore sitting in the ground, and not mining those ores and enriching them is always a choice that's available. Also, there are byproducts which are not less dangerous, that are created as part of nuclear fission, like iodine-131, which does not occur naturally at all.