The ads are administered by Google, so BPL has little control over the specific adverts.
Ads tend to appear for one of three reasons:
1) Google is matching them with the content of this site (ie. Arcteryx, Moosejaw ads)
2) Google is matching them with your personal internet usage.
3) The advertiser has a huge budget and is just advertising everywhere.
The language ads (which I've never seen) are likely appearing because of #2 or #3 - probably 3. Most likely they'll be gone in a few weeks. BPL could specifically ban an individual advertiser, but the advertising world is huge and constantly changing.