The fact that it's Barty Crouch Jr. in disguise; the fact that he claims the reason he is doing it is because Albus Dumbledore wants him to teach it as practically as possible so they know how to fight it in the real world. The fact that Harry Potter can practically beat the curse.

The Unforgiveable Curses are taught in the Sixth Year, per the Defense Against the Dark Arts Curriculum.

WHICH MEANS that Severus Snape, as the Defense Against the Dark Arts teacher in Harry's sixth year, could teach the Unforgiveable Curses. And nothing is said about Mad-Eye performing the curses, so it must be.... OKAY?? to teach the students that way.

Marlene and Emma arguing while lying out together by the Black Lake.

Taken by Lily Evans who was rolling her eyes.

Andromeda after a fight with Bellatrix.

Taken by a worried Narcissa Black.

"The antidote for a blended poison will be equal to more than the sum of the antidotes for each of the separate components."

Golpalott's Third Law is a law for making antidotes, which appears to say that the antidote for a blended poison - that is, a poison created by mixing several other poisons together - cannot simply be created by finding the antidotes to each separate poison in the blended whole and mixing them together.

The potionmaker must find that single ingredient which, when added to the blended antidotes, transforms them near-alchemically into a combined whole which will counteract the entire blended poison. Simply put, according to this law, a true antidote to a blended poison is more than the sum of its parts. 

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