sorry if i was snappy in that post this is causing me headaches (google, not you).
the only way to know where a hit came from is to check the http variable "referrer" normal web browsers "carry referrers" meaning they provide a value that is the last page they were on.
if a normal web browser goes clicks a link from example.com to your site and your site checked the referrer string it would see example.com.
problem with this is that google does not follow links in this way and therefore there is no referrer value to check.
googlebot's traffic from the offending site to your site is the traffic you'd want to block, but it is impossible to tell if google is coming from a redirection or just indexing your site.