If you read the mod maker's actual note, you'll see that they were not "threatened" but rather they entered into a dialogue with a team they respect and want to

If you read the mod maker's actual note, you'll see that they were not "threatened" but rather they entered into a dialogue with a team they respect and want to maintain good relations with (video game mods are often a path to employment in the industry), so they chose to halt development when Bethesda said they couldn't allow it. These conversations can be civil and respectful, even if the outcome is not ideal.