An AT&T Inc. executive told a judge that the company’s contentious relationship with Comcast Corp. is evidence that the two rivals wouldn’t coordinate to withhold content from upstart distributors if AT&T’s acquisition of Time Warner Inc. goes through, as the U.S. claims. John Stankey, who leads AT&T’s merger-integration team and will oversee Time Warner if the $85 billion deal closes, testified Wednesday in federal court in Washington that dealing with Comcast’s dishonest claims about AT&T in some advertisements is like “playing whack-a-mole.” SourceSome downside still holds. $T, AT&T Inc. / D