beat on

Verb

 * 1)  To talk at length; to go on and on; to rant or expound.
 * She's beating on about poor service.
 * 1)  To criticize, impugn or shed a bad light on (a group or topic) for political gain.
 * She's unpopular enough that photos of her are used in elections to beat on liberal candidates.
 * You guys are always beating on immigration, but it won't win you this election.