Immigration is like a marriage.
The potential immigrant chooses Canada and applies to become a citizen (the proposal). Canada accepts the proposal and after some time and paperwork, welcomes the new immigrant as a citizen (the wedding). There's even a ceremony where an oath is sworn. It is a covenant . . . a promise . . . a two sided promise. I, the immigrant promise to uphold the laws of the land and we, Canada promise to ensure your rights.
Covenants can be broken.
A Canadian is not a Canadian when he has broken the covenant.
That covenant is with US. All of us. It is a promise to the people, not to the government and when someone CHOOSES to renounce US, it seems entirely appropriate that we should have the right to renounce THEM.
While it might not seem fair that a homegrown terrorist can't be deported, I'm grateful that those who have opted to remain dual citizens must keep their promises or be booted.
It might seem simplistic. It is. You chose us. Then you turned on us. In whose rationale are we bound and obligated to your sorry ass?