>What would you say about people who knowingly do actions that will lead to widespread harm and future deaths even though they're killing no one directly?

Are we talking about scientists here too or just those who give orders?

Pretty much anything can be used as a weapon and many things can be used for widespread harm.

What if you are working on something that can be used both ways? Spread good and death?

Those people are despicable too. But they are far less common than you probably think.