This entire country has suffered.
The entire world has suffered.
These people did things that warrant the loss of their lives, yet they continue to live and commit more crimes against humanity.
Getting joy out of something good for humanity is natural.
If for no other reason, for the relief of the pressure on the entire human species, like extracting a splinter.
If for no other reason, for the benefit of removing a cancer in our societal organism.
If for no other reason, to celebrate just a mild victory against tyranny.
If for no other reason, to show everyone else planning something that evil will not be tolerated.
Happiness doesn't even begin to describe what we should be feeling about something like that.