This is way out of line and no EMS provider has the right to administer saline for pain. This goes against the standard of care and practically every position out there for pain management. There is no way (unless you have prior knowledge of patients history) of determining in a brief field contact that a patient is only drug seeking. Sure, we may have suspicions but it is not up to us or in our scope of practice to make that determination.
If you truly believe that the patient is BS'ing than you can be passive in your denial by talking more, taking longer to do your assessment, vitals, etc. But again, a patient's pain rating is completely subjective. What the patient feels may not be the same as you would feel. As mentioned, it is a bad practice to try and decide what someone else is feeling.
Who really cares if a patient gets a dose of fentanyl or morphine? If you start to see this patient over and over than yes, you just identified a problem. But first time encounters shouldn't be judged.
I am a great proponent of analgesia and get so tired of out dated attitudes and opinions on using opiates.