Alternatively he might be angry that the overly broad legislation that he was involved with has been used an imperfect way and justified the criticism that it received. I lean a bit further toward getting one over on the Tories though.
Put specific cases in which the law is applicable into the law itself, and specifically exclude as many applications as you can see that it shouldn't be applied for.
Giving broad powers to police and trusting them, just like trusting any human with broad powers, is a recipe for disaster. But then again we all knew this, I'm glad it's been an eye opener for him.
If this was a misapplication of the law then all that's called for is a slap on the wrist for the people who detained Miranda and an official apology. They might get some extra oversight out of it, but that's a stretch. Probably just a few internal memos so future actions don't raise such a stink.
The government doesn't comment on security matters. There is no recourse. End of discussion.