@YukiOnna
It is a prime example of Nazi Germany's genocide of Jews, they did it for petty reasons and then just blew them out of proportion to get the public on their side.
Still met with opposition from whitin the army and also widespread international condemnation.
also hitler was met with several plots to kill him.
@Meridis
I mean, dude, you don't even have to go into history like YukiOnna did. We have enough examples of this TODAY. One of the US's biggest allied dictatorships (US is allied to about 70% of the worlds dictators) just had a big thing where they started letting women drive to show that they are "improving and civilized" but executed all the women who were protesting for the right afterwards. All of that is because protesters are a challenge to their authority.
Not a valid parallel due to the fact it's not a genocide example and even within saudi arabia there's opposition, on the manga there's none of that and what we see is killing witches is an spectacle for the sake of edgyness.
To be honest, since witches are powerfull and having this emperor persecuting nothing, nothing prevents another organization to take advantage of the witches power for their own.
in fact due to the witches power such act would likely trigger a civil war to begin with.