[quote=SkyWithFluffyclouds]
But Tom Riddle himself didn't know he was a half blood when he was sorted.[/quote]

He was still a parselmouth. This, plus his ambition, pretty much guaranteed the hat would place him in the right spot. Descended from Slytherin plus that sort of ambition? 

[quote]Edit: And I would think that after the war they would take steps to be more accepting as it is a delicate subject.[/quote]

The Hat decides. They can't exactly change the hat's opinion. Therefore, no changes.