My take on it would be if you've been let down or had a bad experience with a company then you may outline that experience, without undue bias and truthfully, within the Forum's Retailers section.
Ranting about a company's practices, be they business or ethical, without any direct experience of that company, would be frowned upon.
Discussion on most subjects may also be discussed freely and intelligently within the 'General' section of the forum though common sense would dictate politics and religion should be avoided.