The concept of the burden of proof is a legal concept, not a scientific one. Science only cares about what can or cannot be falsified, without making any sort of preliminary value judgments like "extraordinary claims."
Claims of any nature, then. If I release a paper saying I have any kind of theory then the scientific method requires that I (or someone else who is sympathetic to my claim) provide a valid theoretical or experimental proof that my theory is valid. If I do not fulfil that expectation then it is fair to decide that my belief was not based on any proper reason, and you can choose to think it is nonsense as you wish. You do not need to waste your time proving that it is nonsense.
