What is "used car salesman" about Franklin? Nothing. He is charismatic and is "selling" Penn State. Used car salesman implies he is trying to put one over on people. Franklin is not doing that. College coaches are supposed to "sell" their schools and programs. That is part of recruiting. This is what Franklin is doing. College coaches should not promise things that are either against the rules or that they cannot actually promise (e.g., starting role, NFL). There is no evidence that Franklin is doing either. So, no, Franklin is not a used car salesman.
People shouldn't confuse enthusiasm and charisma with deception. It may make certain other schools' athletic supporters feel better by trying to convince themselves that Franklin is a used car salesman, but of course, that doesn't make it true.