Can't save Himself

I was reading in Mark 15 this morning.  In vs 31 the chief priests and teachers of the law mocked Jesus and said: "but He can't save Himself."  This is true and false.  It is false because Jesus could have come down at any time and saved Himself.  But it is false because He couldn't save Himself or maybe it should say He "WOULDN'T" save Himself.  Thank God He didn't try to save Himself.  He had to be crucified to pay for "MY" sins.