Hello Christian,
Closing topics (like http://forum.bitdefender.com/index.php?showtopic=38160 or others) is not the best way to face negative or even a little bit ironic comments. You have to consider that even these comments are for the product improvement and not for you personally.
Anyway, you have the power to close topics showing to your customers the way...they have to follow. 
My Best Regards!