[Karl Spooner]

It should be simple to prove that he was. Show me the documents. Like I said, the burden of proof is on him.

[Texas Yellow Rose]

So you said,  "Neither parent was a citizen of the US at the time of his birth."

In other words, you have no proof.  Is that correct? 

I'd say, if you are going to make statements like that, the burden of proof is on you. If you can't prove it, don't say it.  After all, it wasn't presented as an opinion.