Holy shit, you are all over the place on this!
Robert initially wanted the remaining Targ's killed when they were children. The discussion you reference with Ned took place in S1 when adult Dany was about to marry a Kahl and have access to an army, much more immanent.
You seem to be confused regarding the idea to kill the babies, was it a good idea or a bad idea?
"Can see why this first Non-Targ to sit on the Iron Throne would want to wipe out remaining Targs" So you think it was a good idea. But.
"any "smart political move" could only be considered smart if it was actually carried out successfully" So now you you think it was a bad idea.
And no, a plan has to be judged to be either a good or bad idea, before any attempt is made to execute it. Because the assassination attempt failed does not change the fact that it was a good idea, poorly executed (so to speak).
@Ares and I had already agreed Robert was an idiot, but he was a badass and he absolutely did make difficult decisions. Missing small council meetings, lol, talking about tax rates, Robert was just smart enough to skip that BS and go get drunk and bang some whores, solid decision IMO.
Now you want to compare Jon to Joffrey, sorry man, you lost me. You have taken a rather simple straightforward idea and Frankensteined the **** out of it, and I still have no idea what you are talking about.
Jon is too much of a boy scout to make hard decisions. He may get the chance to prove me wrong.