We do occasionally run ads in order to keep free services free. However, ads of the nature you describe are not permitted in our advertiser's network.
I did not see that ad when visiting the site. If you do see an offensive ad again, please make a screenshot and attach it to a reply to this message, and provide the URL the ad links to by right-clicking the ad and copying the URL as well as the country you're currently browsing from. We take this very seriously.
Here's how to make a screenshot:
Please note that it's possible for ads to appear in your browser that were *not* placed there by WordPress.com. These ads are sometimes caused by malware or a virus, but more often it is due to a browser extension or toolbar that you may have installed in your browser.
These sites have further explanation and suggestions for eliminating the ads:
Let us know if you have any more questions.