The notion of freedom of speech must keep HR personnel awake at night - not for any overriding desires to promote a fascist workplace, but keeping people clear of the fine line that separates free thinking and workplace disruption.
In the UK, the issue of freedom of speech in the workplace has been brought back into the limelight after the Oxford University Union invited some unsavory characters such as the head of the BNP (a far-right fringe political group in the UK) and a well-known holocaust denier to participate in debates.
To cut straight to the point, the law in the UK is not always clear on what constitutes free speech and what constitutes actionable speech in the workplace. Then there are the realities of the workplace; as this article quickly points out, the very relationship we have with our employees or our managers limits the real "freedom" of speech we have.
Secondly, what might be protected as free speech in the public domain won't necessarily work at the office. For instance, making misogynist declarations in the park won't win you many friends, but it won't have any serious repercussions on your life (unless you get punched in the nose by a passer-by). However, such statements to a colleague may end up costing you your job for harassment.
As far as I'm concerned, the right to freedom of expression is clearly trumped by our freedom to not be bothered while at work. Frankly, the freedom of expression in the workplace argument is clearly one that should be exercised with caution.
We in the workplace would do well to not waste any political or legal capital defending the inexcusable, such as socially unacceptable commentary, and spend more time protecting those who suffer at the hands of abusive expressions of communication or action.