This incident was over shortly after it began. A Subway employee tweeted a selfie, in uniform and apparently on the job, supporting the killing of police officers.
After Subway investigated, the company made the right decision by firing the woman. How do people, at this point, not understand that what you post on public profiles is public? And who would openly gloat about dead cops?
The First Amendment is a restriction on the government, not on individuals or private businesses, and speech has consequences.
What do you think about the social media pressure to fire people who say and do stupid things? Keep in mind, this woman was on the job and wearing her uniform. Does the difference come down to private, off-duty time and on-the-job antics?