Basically Pietro wanted to save Wanda's life, right? And didn't care who got hurt in the process. (Why did Magneto kill him?) As far as reasons for doing bad things go, wanting so save your sister's life isn't the worst one. Not that I approve, but I also don't hate him for it, and now I want to read Wanda&Pietro post-House of M fic.

(Also, wtf Xavier? There's at least one reality where her children existed, even if they were erased later. Great job helping the woman having a breakdown. The more I know about him the less I like Xavier in the comics.)