Kindly keep the materials you host on your subdomain(s) safe for work. Inappropriate web sites, if found, will have their subdomains/accounts suspended. If you are thinking of blocking 6b5.net entirely due to a single web site or domain name on it, consider blocking the offending subdomain itself and notify the administrator via e-mail about it. You don't need to worry about unblocking the subdomain later, as abused subdomains do not get put back for re-registration.