I believe what Jonathon Turley wrote yesterday in The Hill pretty much sums this impeachment process up.

"These “agitated passions” will not be a substitute for proof in an impeachment. We currently have too much of the former and too little of the latter."

Not a Trump supporter but just as highly regarded legal scholar as the others called to testify within minutes of his testimony against impeachment his home and office was inundated with hateful rhetoric and threats from the left. His testimony is similar to many other legal experts who have worked impeachment cases of Nixon and Clinton, the evidence is just not there and the process is skewed.

Therefore it is pertinent when you have past democrat and republican legal scholars/experts/attorneys involved in prior impeachment processes in concertation with one another on this impeachment process being flawed to bring forth any potential conflicts of interest/bias by witnesses called who say otherwise.