The 1st Amendment protects you from government punishing you for what you say. It doesn't protect you from punishment by employers for violating their rules regarding conduct both on and off the job, and it doesn't protect you from the court of public opinion. The team felt that Guillen, in his position with the club, hurt the team. After his remarks, attendance at games dropped, and never recovered to the levels before he opened his mouth. You do something to anger your customers, that is justification for losing your job - which he did at the end of the season. He got five games and that wasn't enough to mollify the angry fan base.