Fairly, less fairly or unfairly. It absolutely can. And I believe he knows that. We should all expect to be questioned and facts checked.
Did he conduct himself inbest possible way? Probably not. That alone might not be fair request for anyone though.
Also, these accusations did not fall out of the sky, but it was reaction to some questionable content.
It would be best, if the conflict went this way:
"Danno:
given the past mistakes I have found in your response,s I do not trust your data enough. Could you please provide original RAW files? Thank you."
"Donald: Sorry to hear that, it is uncomfortable. Here is the data".
"Danno and rest of the forum on their merry way".
But that didn't happen, did it?
Donald claims to make no such mistakes, presenting authority over others", Danno fights back. What course do you expect?