In House of M #1, Wolverine and Emma are the only ones who say that Wanda should be killed.
Xavier says he can't. Emma asks Strange, who says he's still researching.
Yet...
Wolverine is still trying to protect his son Daken, who's a rapist, a murderer, and an all-around scumbag.
And in X-Men: Phoenix - Warsong, Emma swears revenge on the Phoenix entity for wiping out all the Cuckoo clones (with the exception of the Three-in-One), despite the fact that Sublime had created them to destroy mutantkind and that they had almost done so beforehand.
So why is it okay to kill Wanda but not Daken or the Cuckoos?