The student doesn't have a "right" to a letter of recommendation. This is something that the professor may or may not give. What you seem to be asking is that letters of recommendation be entitlements. Conservatives used to believe that rights were different from entitlements.
A right is the freedom to take an action. Rights to not compel others to give in to your wishes. If the government were to tell the student that he may not belive in Creationism (and threatening him with jail or death), that would be denial of a right.
The student doesn't have a "right" to a letter of recommendation.
I have repeatedly explained on this thread that the right has to do with not being discriminated against based on race, gender, age, religion, etc. It does not have to do with a right to a letter. That is a total fabrication. It is not a right. Please see my post to Nebullis at 395
The a) and c) points are contained in this paragraph I posted at 329
If either a) or c) are true then the government has a substantial interest in protecting the student's rights under the Constitution. If any of these are true, the student has good cause.