You are misrepresenting the situation. The debate isn't about whether they should go with another vendor or not. Everybody can agree that they would have the right to pick a different vendor. That's not what they're doing, they're instead trying to force Anthropic into doing what they want by applying a designation previously only reserved for Chinese companies like Huawei as punishment for taking their stance, with an unspoken agreement that if Anthropic backs down and allows full usage then the designation will be removed
The Pentagon does this kind of thing all the time. It's just usually not this official.