The Hatch Act prohibits federal employees from a number of things. One of those things is that, while being paid by you, the taxpayer, I am not allowed to make partisan endorsements of candidates.
Now, I believe that 45 is not a candidate right now. He won the election last November. However, I believe he has filed paperwork for his 2020 campaign.
To be on the safe side, I try to not make partisan political remarks during the hours I am at work. This has been specifically interpreted by the FAA to prohibit retweets and reblogs of partisan political remarks.
I do, occasionally, reblog or tweet or link to a news article from the BBC or CNN. I, personally, do not believe that saying true facts about events can possibly be a partisan political remark, unless one party is stating that truth belongs to one party and the other party is nothing but lies.
But since I am currently at home, and not on the taxpayer dime, I am entitled to my opinion as a citizen, and can freely say the 45 is a goddamn idiot.