Why would a relatavist, in particular, talk about the burden of proof like that? Why is that in any way related to whether you are a relatavist or not?
Burden of proof is a function of the scientific method, nothing to do with relatavism.
Amusing that you say gravity- seeing as gravity is 'just' a theory and is very far indeed from being absolute. 'Gravity' is a name we have given to explain certain sorts of behaviour, but we cannot outright prove any of our theories about it.
Meanwhile...
"Proof isn't relevant to proving an argument?.."
Well, you say to a relatavist that it is... the relatavist just says- how do YOU know? You are just a being of flawed perceptions, if you even exist at all; you cannot state such things with truth.
"You saying that they are invalid, doesn't make them invalid. That is my point all along. I have evidence to substantiate my claims. You do not. Simple as that."
Your evidence is based on your perceptions, your perceptions might be flawed- simple as THAT. Hence, you have no greater reason to say you are definitely right. There is room for doubt.
"Which invalidates the who concept of sceptism. It has no effect on anything that takes place in the natural world. It doesn't change the laws of gravity. It doesn't change the reality around us. Simple as that."
Just because something has no apparent application, that in no way invalidates it. I would have thought that was obvious.
"Doesn't change reality..regardless of a theory existing ..it doesn't do any good if their is no substantive evidence to support it."
Who the hell cares what 'good' it does? If it is so, it is so; you were saying it was some sort of nonsense idea, when in fact it is a whole area of science that physics is looking into.
As it is, in explaining some of the stranger behaviours of light, it could end up being very useful and relevant indeed.