You're the one who said you followed thru two layers of links to get to the site...
Were none of the other links suspicious?
That aside, did you warn the posters in the other thread to be careful about the links they follow from the
given link in that discussion?
I just did a google search on
"reporting websites anonymous", and the first two hits I got appear to
be sites that may suit your needs. Note that one of the sites states it is sponsored by legitimate
adult sites as an effort to get rid of the more shady operators out there, if that bothers you, you
may have to consider not using thier form. The other site is a watch group in the UK; but in both
cases I recommend you read thier FAQs, to be clear on what needs to be in the report.