For regular run of site ad buys, you're right. And a lot of CMS and ad systems come with a way to flag content as sensitive. For a small ad buy, nobody cares that much.

For big campaigns - bread and butter for print and web - different story. These are carefully designed in-your-face takeover ads and the brands care much more how they're presented.

The bigger problem is ad sales for newspapers is usually just AdSense backfill or national sales from the parent company. The former is just beer money unless your publication is NYT size, the latter is drying up because there's nobody to sell to!