Do you know what independent means?
Public servants serve the public. They do not serve the President/Governor/Prime Minister/Premier, etc.
I haven't heard Comey state that the loyalty request from Trump was to him personally and not (or at the expense of) the country.
What Comey stated this morning that was given very little replay was that prior to his first meeting with Trump he made the determination that he didn't trust the President so he decided to take notes on his conversations (even though he had not ever done so with Obama or Bush). If you dislike and distrust your employer then chances are the feeling is mutual. Trump had every reason then to challenge whether Comey was up for the job and fire him if he didn't it was the case.