This is crappy analysis and just plain WRONG. Trump can fire Mueller if he doesn't like his haircut. No reason needs to be given. It means nothing about "obstruction."
Legally and judiciarilly you’re correct.
But as Rush explained yesterday, it is political.
The Congress has always had the power to impeach the president for any reason. Just as the president can pardon anyone accused or convicted of federal crimes—for any reason.
Now, no where in the Constitution is there ANY definition as to what “high crimes and misdemeanors” are in reference to the president. Up to this point, the president would had to have done something beyond politics to get an impeachment going. So here we are, and it the Congress, not Trump, that has to decide whether they cross this Rubicon.
The glorious thing about the past 225 years of this Republic is no one in either party has tried to use impeachment to undo an election choice made the voters.
Until now.
Trump should fire Mueller. Just do it.
If the Congress decides to impeach him for that, then we’ll all have to deal with the outcome of how THEY—the Congress—killed the American Republic.