Well, that should say something to ya... that PA is a well known AVS and popular with the spoofers. No different than the top paysites with password trading. If it's popular, there are pass requests. If the webmaster thinks this is a major issue, it's down to them to secure their sites. I've been on spoofing lists, can't say I burned a noticeable amount of bandwidth.
ACK
"how come pro adult has not done anything to combat this probelm if it's true?"
They probably don't class it as a major problem. Most of the spoofs involve their own servers, so it's their bandwidth. If it's one of your servers being spoofed, you can protect it.