I really don't understand why this is a difficult concept for people to understand.
I pretty much assume MI6 is spying on me as well, but I don't care - because they don't have jurisdiction over me. The NSA or CIA spying on me? That's an entirely different story.
It's incredibly naive to think nation states will not spy on each other - allied or not. Alliances change on a whim, if you have a spy agency it'd be criminally negligent not to spy on your allies.
When that intelligence is redirected and used to control internal politics? Now it's a problem.