Big hearing today where a House committee grilled the Deputy Attorney General about tweets/emails between two FBI agents. In one or more Trump was called an "idiot". This arguably reflects adversely on the agent and might indicate a prejudice which carried over into official duties.
While I never had the position the agents had, being lower on the totem pole than they, I too used to call the president an "idiot". In my case it was Reagan, not Trump, and technically I called him "the senior idiot" (reflecting the fact I was calling my immediate boss "the junior idiot". But I'm not aware that my dislike and low evaluation of Reagan ever affected my performance. As a matter of fact I got an award (cash, no less) for my work in implementing the most controversial program ASCS handled during my time with the agency.
It's impossible to tell with the agents. But in my experience the ability of people to compartmentalize and to deny is what separates us from the rest of the animal kingdom.