That is a very good point about Joker going after people he's sort of fond of. IIRC, in Batman #14 there was fairly explicit confirmation that, in his own twisted way, he's in love with Batman.

Right, he loves Batman, he really likes the Bat-family, he admires the commissioner, it’s just that his love is evolved and sometimes fatal.

Even when he kills his henchmen, he always picks his favorites and is nice to them before the deed.