To be fair, I dislike Morrison's Joker, too.
As for White Knight, as far as I am concerned anything set in out of continuity stories is fair game (I love a good Elseworlds/What-If/Imaginary Story) as long as it's an enjoyable read. WK is a fun story that explores things I never want to see in an in continuity Batman comic. If it were supposed to be canon, my opinion would be very different.
"Sane pills" (a perfect description, btw) are fine for this type of story, as it gets us to a repentant Joker quickly so the plot can move from there. That said, I have a high tolerance for comic book nonsense. My second favourite comic book character was bitten by a radio-active spider that resulted in a series of incredibly inconsistent powers. I mean, Batman himself regularly fights a crocodile man.
All writing (and art) is, to one degree or another, a self-insert. I don't know anything about Sean Murphy outside of his comic book work, so can't say how close his Joker is to his personal views, but I rarely base my enjoyment of a work on it.
"Has Sariel summoned you here, Azrael? Have you come to witness the miracle of your brethren arriving on Earth?"
"I WILL MIX THE ASHES OF YOUR BONES WITH SALT AND USE THEM TO ENSURE THE EARTH THE TEMPLARS TILLED NEVER BEARS FRUIT AGAIN!"
"*sigh* I hoped it was for the miracle."
Dan Watters' Azrael was incredible, a constant delight and perhaps too good for this world (but not the Forth). For the love of St. Dumas, DC, give us more!!!