How come this sentence そんなことでどうする？ takes on so many forms?

Question

ロニキス

「はは。クロード、これしきの事で怯えているのか？少尉ともあろうものが、そんなことでどうする？

The context is that Ronixis is a commander who hands Claude a pistol and tells him to use it in case of an attack.

I'm confused at exactly what そんなことでどうする？ means.

On one post そんなことで means "such a (little) thing".

Someone on another site wrote to me that: Kind of hard to explain since it's an idiom, the literal translation would be "what will you do when you are like that? " and it's a phrase used when you expect more from the person you are talking to.

Answer 1

こと refers to something intangible. This そんなこと refers to クロード's current condition/situation/appearance. で after it is a particle that marks a condition/situation/cause (like with or in in English). どうする literally means "what do you do", but here it's a rhetorical question that effectively means どうしようもない/どうにもならない ("it's helpless", "you can't do anything", "it gets you nowhere", etc.). Put together, そんなことでどうする roughly means something like "What can you do if you're like that" or "You're useless in such a condition". Nevertheless, this is indeed a set expression (if not an idiom), so you can remember it as-is. Likewise, if someone says こんなことでどうする to themself, it means something like "This (situation) is not good, I must do better".