What is Freedom of speech in the work place?

The guarantee of freedom of speech and the press apply to government limits on your freedom, not your employer's limits.

For example, if you work at Gimbel's department store, the government could not stop you from wearing a shirt that advertises for Macy's, but you r employer could.

Essentially, because you are free to find another job, your employer can limit your activities in the workplace in ways that the government is not allowed.