Both sides should be able to make positive statements and provide logical support.
This is basic.
If you constantly attack without making any positive statements and refuse to clarify your criticisms when paraphrased (Nuh-uh that's not what I said, go back and read the words and prove it, you can't prove me wrong!) you are hiding behind the massive and very blurry wall known as the ambiguity fallacy (also known as the appeal to ignorance).
These individuals may (or may not) have a coherent position (as they often repeatedly claim in vague terms and bald assertions), but regardless, inexplicably refuse to communicate.
They mistakenly believe that the darkness gives them the benefit of the doubt.
They believe that if they can merely cast doubt on certain obscure peripheral details of their opponent's argument (or pepper enough ridicule and ad hominems into their diatribe), then they are automatically proven correct without ever having to state their own argument.
However, based on epistemological standards of evidence, they do not have the benefit of the doubt.
You must show your logic, because without evidence to the contrary, your position is logically incoherent.
I call these creatures the "Gingerbread Men".