Despite the mistaken assumptions of inadequately educated Leftist feces throwing monkeys, government buildings are generally speaking not "free speech zones" for the employees who work at them.

Yes, the Hatch Act is part of it:

"The Hatch Act is a U.S. federal law limiting the political activities of executive branch employees, D.C. employees, and some state/local workers in federally funded programs, aiming to keep government nonpartisan and protect employees from coercion. It generally prohibits partisan political acts (like campaigning, fundraising) while on duty, in a federal building, or using government property, but allows many off-duty activities like voting, expressing opinions, and joining parties."

So every year, and especially during campaign season, employees get short lecture on no political activities or talk, and the Unions give one too. I disagreed with the Union, they would tell you not to participate in any, even peaceful, demonstrations. That if you get your face plastered on the front page carrying a sign, they may not be able to help you. As a result I was one of the few activists, and all I did was hold up an Obama sign on a street corner. Not much activism.

I did enjoy the leftist loons there, but when one fellow asked me to go meet and talk to hardcore leftists, communists, etc., I begged off. I knew employer said "NO", and that was it.

They are controlling what is being said or written on government property paid for by the taxpayers dime.

They are inhibiting behavior beyond that as I explained above. The employer doesn't want you involved with radical groups, doesn't want to find your face plastered in the newspaper just for being at an event. I canvassed in precincts, but I understood that if I were shot at during canvassing and it got in the papers, that I was going to have to explain it to my employer, and the explanation might not work. Especially if my name and pic got into the papers. This was the big warning from the Union.