Here’s a link with more information.
1. There’s a difference between freedom of speech and slandering other people. Not having seen the comments myself, I assume they cross over the line of what’s generally socially acceptable behavior.
2. Police officers are supposed to be leaders in their communities and set good examples. Such behavior is not becoming of an officer or community leader.
3. In general, people get into trouble whenever they are shown to be racist or bigoted, not necessarily just because of Facebook (I’m reminded of another recent event where a woman was fired for forwarding a racist Obama joke via email). Facebook has only made it easier for people to express themselves, and sadly, many people do not have a suitable filter between their minds and their fingertips. As time goes on, people will wise up about what’s appropriate to post and what’s not.