It is a security risk. That's the problem you create if you allow every single vendor from imposing their own rules. The contracts are not awarded because doing so would create a security risk.
I don't know what analogy would drive the point home. Imagine a password management system where the people running the company have an ideology that leads them to believe that their system should not allow anyone to secure anything used in military applications. Well, that's a security risk. And no contracts should be granted. Cause and effect. There's no confusion here.
OK. I'm imagining such a password management system. I don't see why it makes sense for the government to ban Microsoft from using that company's password management system for Minecraft, just because Microsoft also happens to sell Microsoft Office to the DoD.
I don't know what analogy would drive the point home. Imagine a password management system where the people running the company have an ideology that leads them to believe that their system should not allow anyone to secure anything used in military applications. Well, that's a security risk. And no contracts should be granted. Cause and effect. There's no confusion here.