The nuttiest thing about the Supreme Court and presidential immunity?

I haven't had much time to read too much about the judgement yet, but I have a couple of initial gut reactions:

 a.   In one respect, it feels a bit like what was a de facto immunity is now a legal immunity.   I mean, haven't we all felt that some things done in the international arena by Presidents past would be criminal if done by anyone else?   Assassinate a foreign leader - or attempt to do so?  

b.   The difference is, though, while we have become used to the idea that there is a very broad scope of what can be "actions in the interest of national self defence", we have never thought the same about internal actions against perceived internal enemies.  It's the difference between, say, how Putin deals with critics and rivals, and how American Presidents respond.

c.    OK, so we put it down to a rubbery concept of "official actions" of a President:

d.  And here is the craziest part of the decision:  

So:

Future Deranged President:    "Attorney General, can't I just get the CIA or FBI, or that sheriff's group who love me, to take out a few of those key politicians who clearly don't have the interest of America at heart, like I do?    I mean, if you're not loyal to me, you're obviously a danger to this great country."   

Attorney General:   "No, Mr President, we're sure no court is going to read 'official act' that broadly".

Future Deranged President:   "What would you know, I'm getting on the phone to FBI Director Bannon".

Later in court:

        Judge:  "No, you can't introduce evidence of the advice the President got - seeking                                             advice is an 'official act'"