Donald Trump (All General Trump Conversations Here) I want Alan Dershowitz to testify as a witness/expert opinion regarding the constitutionality of the current impeachment process.
I think Trump is guilty.
Professor Dershowitz would surely testify that the founding fathers were very careful about what counted as justificatory ground for congress to impeachment a duly elected president. Mr. Dershowitz would surely agree that the framers of the constitution did decide, after careful debate - much of which Mr. Dershowitz spoke about earlier - to include the ability for Congress to impeach a president under certain conditions.
These conditions are vague, as they are meant to be. However, I think the professor would readily agree that the framers did not intend for the president to be able to invoke executive privilege as a means to impede an impeachment proceeding already in progress.
I'm sure the professor would also readily explicate upon the differences between other president's invoking it and this one.
As if it's not just been done. None of the other presidents invoked it as a means to block testimony into an investigation of their own impeachable behaviour - as determined by congress.