I refer to this regulation, lasting until the very end of the war but not after, so clearly it was enacted with the war in mind. Even habeas corpus was suspended, and that doesn't normally happen.
So, putting aside the fact wars make everyone frantic, how else could it have been handled? It's not like they were tortured, as opposed to what fascist dictators like Assad do especially in a war.
There is also 'Haw-Haw' who seemed at best misguided, barely effective even in his chosen profession of propaganda, but capital punishment? The last to do so for treason, which seems to have been abolished in the states, but it's not like they don't get their share of people encouraging other nations to attack... and it's not like Joyce was in Hitler's cabinet, who were also sentenced in Nuremberg... there is just no differentiation between words and actions. Note that this was a Tory right-wing government imposing upon the far-right, which makes it an interesting historical juxtaposition and wonder about parallels in other countries and times. So, how do extreme political situations deal with extreme ideology?