Guilt by association is necessary.

It's not that people in the past were fools
when they punished three generations.
Without such a community, it wouldn't be a human society,
and without condemnation,
reflection or laws would be meaningless, leading to lawlessness.
It might have been excessive at times,
but it wasn't execution;
as for those saying that the act of punishment itself is wrong,
we should kill them first. If you were born under pro-Japanese ancestors,
you should be punished,
but are you being punished now?
If you aren't, the state is showing you immense favor.
You should just shut your mouth.
If you don't shut it, then accept your punishment. Furthermore, world-renowned scholars all agree with the concept of guilt by association.