I'm being serious here: Why would the Democratic side be opposed to the Bidens testifying? The justification they give, is that Joe/Hunter don't have relevant information regarding Trump's actions in Ukraine. And this is true. They do however have information regarding their OWN activities in Ukraine, which was center and front of Trump's actions. If they are able to testify under oath that all of their various activities were on the up and up, it would be a very damning drawback to Trump's argument that he was inclined to investigate a national security issue(wherein a former VP may have engaged in a quid pro quo to protect his son.). The Bidens's testimony could very well actually win the case for the Democrats. If they can conclusively proof their own lack of wrongdoing, the onus goes straight onto Trump. Especially if they were made aware to the DOJ and others that there was "no there, there." The Democrats need to prove two things beyond a reasonable doubt: 1) That Trump elicited to pressure the Ukrainians to open up the investigation. Or 2) That Trump never had a legal basis to investigate to begin with(Just like the FBI's Crossfire Hurricane) The Bidens are very much material to #2, and it's a much easier avenue for Democrats to win.