Did the emp do the wrong thing with Angron? Probably, but no worse than Magnus, Angron was 1/2 khornate berserker already, Magnus tried to warn the Emp and got attacked bc "no way would horus do that!"
Because they're all crazy heretics! We need to leave this galaxy Orks can at least be reasoned with in the other galaxies, tell 'em where all the good fights are and we have a galaxy to ourselves.
Why don't we tell them to fight the Tyranids approaching this galaxy? That way orkz will clash with the Tyranids, both threats are eliminated, we have the galaxy to ourselves, everyone's happy, it's a win win.
Yes he did crazy wrong thing, Butchers Nail could be removed . He humiliated Angron , and created a monster , Emperor warned Magnus not to USE sorcery , Magnus would be a Hearth of Astronomikon , and Emperor would fight in other realm to defeat chaos Gods , but Magnus by hes own fault destroyed emperors decade work , he thought that he is more powerful psyker than Emperor himself , and thought that only he knows of Horus Heresy . He was to proud .
We got noise marines for a reason i guess and we like the sound of tortured voices that scream out in anguish around the fields. Perhaps.
But someone HAS to win that fight and if Orks we got crazy bad-ass Orks or we got Tyranids that have absorbed so much Ork they've become Orkanids and then we all are royally and truly fucked.
If you read Fulgrim, the noise marines were addicted to create the perfect sound that they had heard in the temple of Slaneesh. Which turns out to be torture and pain, because of course this is slaneesh.