I imagine if you offer your opinion about the price in a professional context where your opinion can affect the actual value of the property then you might have to follow some rules.
If you drive by a house and say "this house doesn't look like it's worth shit" you're probably not going to wind up in court after someone complains that said house is worth quite a bit more than shit and you're driving the price down.
Laws actually can be vague while remaining Constitutional. Sometimes it's unavoidable. Court cases can be used to refine the edges.
Actually this has come up before with a similar law in Arizona, where the state tried to ban Zestimates. Volokh's analysis basically agreed with me (http://volokh.com/posts/1177792494.shtml). Though I couldn't find any info about what ultimately happened with that case.
There was never an actual legal case. There were just cease and desist letters with threats of a case. Before any actual legal case could materialize the law in AZ was changed to allow automated appraisals without certification as long as no money changed hands for the appraisal.
If you drive by a house and say "this house doesn't look like it's worth shit" you're probably not going to wind up in court after someone complains that said house is worth quite a bit more than shit and you're driving the price down.
Laws actually can be vague while remaining Constitutional. Sometimes it's unavoidable. Court cases can be used to refine the edges.