Dan Drezner has a good post that is worth a read. Again, I think the issue he's discussing raises the question on how some of these lower-level actors fit into the policymaking process. This piece also sort of raises the issue of how these actors should fit into the broader public discourse over policies as well. But I suppose my advice to Senator Graham would be, if you're not prepared for, or don't want to hear the answer, then don't ask the question. Unless you're purposely trying to bait the DNI to bash him, that is. I agree that it's ridiculous to feign this sort of outrage and demand the resignation of a public official who is—dare I say it? Actually attempting to do his job in an unbiased manner?
As an extension of this issue, I have to wonder what sort of political capital there is to be gained from publicly attacking the DNI in this way? Does Graham impress voters? Colleagues?