They are often a great source of material which can be freely plagiarized without attribution.
In this case, however, there is nothing worthy of plagiarizing.
I sometimes cite 'em anyway. They're at least as valid as a law review article or practitioner's handbook.
Going strictly on the text of the opinion - with no access to the appellate record - this decision seems alright to me. When you're on the clock as a public employee, your free speech rights are somewhat curtailed. Looking at the District Court case (2005 WL 351743), it should be noted that the plaintiff of this case was not prevented from expressing her views on marriage or gay rights outside work, over lunch, or on break. All she was instructed to do was, if she was going to use the City's email system to advertise her group, she had to remove verbiage that could be offensive to gay people.
This all goes back to my central First Amendment theorem - freedom of speech does not guarantee access to a forum. When the government provides a forum, you gotta play by the government's rules.