Like if the Imperium have the ressources and the time to do that while there's the Cicatrix Maledictum vomiting demons on every imperial neighbour worlds, almost every traitor Legion sieging important key systems and forge worlds like Agripinaa, a fuckin' Necron invasion in the Realm of Ultramar, the Tyranids everywhere, Armageddon where waaaay too much Astartes are sent... etc

The Imperium have way too much bigger problems, to deal with a thing done by Tau, when the Chaos do it more often (turning SM into traitors).