It's ethically untenable.

Meaning

It's morally unacceptable.

Examples

• John: I'm considering accepting the bribe.
• Alice: John, that's completely wrong. <b>It's ethically untenable</b>.
• John: But the money is significant.
• Alice: The consequences would be far worse. You can't justify this; <b>it's ethically untenable</b>.