This is a problem we've all had to deal with before. You blog about fishing and your targeted advertising is all about spa treaments, or puggles (God forbid), or Head On.
It wouldn't be that big of a deal except that your readers are interested in your content, and when your advertising doesn't relate to that content, it's less likely to interest your readers.
So what can you do?
Copy down the url of the offending advertiser, log into your AdSense account, and add that url to the filter list.
Within a few hours, the filter should take effect and more relevant advertising should be available to your readership. Everybody wins!