I think what might be going on with this objection to the Comey firing is to try to build a narrative of Trump saying “you’re fired!” It’s lame, but I think that this might be the foundation of an appeal to people 18-25ish. There seems to be a belief that one should do what is right in one’s own eyes and that employers are required to negotiate with employees who may view work assignments as being ala carte.
The GOP could probably ruin this now and for the future by explaining the situation in terms of why it doesn’t work for an unelected official with so much authority and power over the rest of us to be a law unto themself. Comey offers such a teachable moment because he has been responsible for so much chaos that we can see. Did Comey fire people for insubordination? Hypocrisy is never attractive.
In this case, Trump is not able to issue a pardon to Flynn, ending any investigation, because Flynn didn’t commit any crime to pardon.