"Scrutiny might be warranted and prudent but assuming that Jihadi John is a British citizen, he should have the same rights as any other British citizen."
Last time I checked, murdering people and inciting racial and/or religious hatred are against British law so Jihadi John and his cronies have chosen to ignore the protections said laws offer other people. And if they think the law doesn't protect others then they should not expect the rest of us to let them hide behind those same laws. Either the protection exists or it does not.
Jihadi John and his "friends" think it is acceptable to kill people just for disagreeing with them, so by the "same rights" logic it is more than acceptable that they should be targeted with extreme prejudice too...
"Do unto others as you would have them do unto you" and all that.