to be fair to the theory though, This wasnt just anyone telling him this...it was the President of the United States..
I don't think it matters that much
as a pro-athlete, you're pretty much a celebrity. You face negative news almost everyday, and as a professional, you learn how to ignore them.
I mean BECAUSE its the president of the US, it might affect him a little bit more than usual, but that shouldn't leave a scar in him.
Like most of the people have said, if that was true, Rondo's performance in NY and Miami series (pre-elbow injury), would've stopped him from being effective.
Instead, we saw a guy who kept racking assists, still blew past people and came back after a gruesome injury
Rondo's a competitor and keeps fighting to improve, so it may affect him at first, but now i think he might use it as a motivation