I don’t think “were evil” is actually a secret, most Death Eaters are known—they plead being under the Imperius or otherwise forced to join, but I don’t think there is much doubt for who was on which side of the war.
As for telling them publically, it’s true it’s not the best way to break the news, but I fear attempts to tell them in private could have been ever worse—with rumors propagating in the school, the fact you can’t tell them all at once and have to take turns and everyone will see something is going on.
In the current situation, it seems an acceptable way of doing it.
Edit : forgot to refer to the “Voldemort—tried to revive—he summoned Death Eaters and he killed them, stole their blood and life” line of Harry, which is why rumors and doubts were likely already in full motion, justifying a clear public announcement as soon as possible.
I don’t think “were evil” is actually a secret, most Death Eaters are known—they plead being under the Imperius or otherwise forced to join, but I don’t think there is much doubt for who was on which side of the war.
As for telling them publically, it’s true it’s not the best way to break the news, but I fear attempts to tell them in private could have been ever worse—with rumors propagating in the school, the fact you can’t tell them all at once and have to take turns and everyone will see something is going on.
In the current situation, it seems an acceptable way of doing it.
Edit : forgot to refer to the “Voldemort—tried to revive—he summoned Death Eaters and he killed them, stole their blood and life” line of Harry, which is why rumors and doubts were likely already in full motion, justifying a clear public announcement as soon as possible.