So now we know why he said this. Trump's panic:
"I would love to send Ambassador Sondland, a really good man and great American, to testify, but unfortunately he would be testifying before a totally compromised kangaroo court, where Republican’s rights have been taken away, and true facts are not allowed out for the public...."
Obstruction. Plain and simple.
It is obviously Trump who is afraid of the "true facts". When he discovers that flattery didn't silence him, Trump will be calling Sondland a liar. Guaranteed.