Damnit I clicked that thinking it would drill down or something, not load the page. Sorry, IT.
I guess now we know why it's there - collecting traffic.
At time of writing, pornhub.com has 69 referrals - I suppose someone was just having a laugh.
It's not uncommon for people to spoof their referrer headers to a site they want to promote or to shock content. Back when I used to track referrers in my access logs, I ended up watching the Simpson's Couch Gag "You're Next" episode because it showed up at least 50 times, for instance.