そんな愚かなことを言うな。の英語

Do not say such foolish things.

Don't say such foolish things.

It would be ill-advised to take such a step.

It is the height of folly to do such a thing.

It is the height of folly―folly itself―to do such a thing.

Don't be a fool.

How foolish!

Don't talk rubbish!

Don't be stupid.

Your views are absurd.

it is all patently nonsense

Don't say stupid things!

Stop your nonsense.

Don't be silly.

Your views are absurd.

of a person, the characteristic of pigheadedness

It is way too stupid.

I know better than to be believe such a rumor.

Don’t say it in a way that causes misunderstanding.

He is an egregious ass.

Don't even say that as a joke.

That's absurd.

That's crazy.

That's impossible.

a damn fool

Though he may be a dunce, he must be aware of that.

a bloody fool

It is a cock-and-bull story.

How can you say such a foolish thing?

How can you say such a foolish thing.