Can I respond here?
I don't agree with Piper's stance, either...but I think it's more nuanced than what many (including you) have made it.
Jesus made a very radical statement that has to be directly dealt with :
Ye have heard that it hath been said, An eye for an eye, and a tooth for a tooth:
But I say unto you, That ye resist not evil: but whosoever shall smite thee on thy right cheek, turn to him the other also.
And if any man will sue thee at the law, and take away thy coat, let him have thy cloak also.
And whosoever shall compel thee to go a mile, go with him twain.
Give to him that asketh thee, and from him that would borrow of thee turn not thou away.
Matthew 5:38-42
And there is a statement in the book of Revelation that says those that live by the sword will have to die by the sword (Revelation 13:10). The principle there is clear - with what measure ye mete, it will be measured to you again (Matt 7:2).
You say that the only evil Jesus was talking about was religious evil - but nowhere in His statements does He make that distinction. In fact, when He spoke of being forced to carry a burden one mile (and you carry it two), it was very non-religious. No doubt you know that the Persians had a law that if you were approached by one of the King's messengers, you could be compelled to assist the messenger for a short distance. Jesus is speaking here of going beyond the law - so how is it we will rest only on the OT law and use that as our defense in this situation regarding armed defense?