A lot of people misinterpret what "freedom of expression" means.
People believe they have the write to "express" themselves as they please in the workplace. That simply isn't the case. Our rights -- our freedoms -- are protected against government interference not private interference. Your employer -- even a government office -- can silence you. There are laws for the workplace that take precedence over your rights. The law protects employees against being discriminated against or being harassed because of their ethnicity, religious beliefs, disabilities, sexual orientation, and gender. Those aren't rights, however. You don't have a right not to be harassed. You are protected by laws.
Quite simply, these officers are out of line, and have broken laws. They don't have a choice but to change their behavior. If they want to frequent this site from home in their private time that is when their right to express themselves is enforceable. However, we all know there are consequences to actions in our private lives as well. But trying to make people behave to serve their best-interest is just a futile effort at protecting "stupid."
The comments about this story are already ridiculous (search news.google.com, and blogs.google.com). Everyone thinks they know their rights, but I can tell by the comments none really know what their rights are, or what a right is.