I'm going to make a very brief statement here.
There is no reason why a question cannot be asked of a brand, especially if they are represented on here, however, any contentious statements need to have evidence associated with them. We have removed posts that are clearly treading a fine line, and I would warn any forum participant that should any legal action take place against the forum as the host of such a comment, we would also have to hand over details about the poster. This includes a great deal of detail about that person that the ISP logs.
Hiding behind a username on a forum does not exonerate you from real world responsibilities and while the admin team tries to ensure an orderly environment, you are responsible for what you post and should it be considered libellous, brands can and will seek redress.