I’m bored, so let’s break this down.
If he did nothing wrong, the relevant question is why shouldn’t he?
Attacking an American patriot. Good job! 
More attacks on an American patriot. Coupled with some nonsense about there must be a quid-pro-quo to meet with investigators looking into possible crimes. But for sake of argument, if you did nothing wrong, then what’s in it for you is to conclude the investigation and allow the investigators to prove your innocence to the world. That is done by meeting with them.
If he did nothing wrong, then he gains a report put out by thorough investigators exonerating him.
More attacks on an American patriot, but this time done to defend Trump’s apparent inability to tell the truth, even while under oath or speaking to Federal agents. That is a weird way to defend someone, by acknowledging their inability to be honest.
Another fabricated attack on the integrity and character of a man who devoted his life to defending our nation and the rule of law. You really must hate Law Enforcement Officers. Wow.
If he is innocent, to have these investigators release a report validating your innocence.
Okay. Let’s not.
Um…straight to the deep state conspiracy theory already? Where is my tinfoil? I need to prepare.
Completely false. But also a little on the crazy. Well, actually, a lot on the crazy.
Bwahahahahaha. No one believes that for a second. 
You don’t seem to have even a rudimentary understanding of how criminal investigations work, do you? Maybe that is why you despise Law Enforcement Officers so much?
The Special Counsel has already given Trump’s legal team the reasons for the interview, and the subjects they want to discuss with him.
Not until the investigation is over. There is no reason whatsoever for anyone to see the details of an ongoing investigation. You just want this as more reason to run defense for Trump. It is typical of a cultist.
Nope. This investigation is still a long way from its conclusion. Look at other similar investigations and their lengths of time to completion.
This was pretty mediocre at best. I give it a C- for effort and a D+ for originality.