Four of NBC’s owned-and-operated TV stations have declined to run ads for Sling TVDish Network’s Internet-delivered television service — and the satcaster has pounced on the issue, accusing Comcast of unfair tactics.

An NBC rep confirmed that stations in New York, San Francisco, San Diego and Washington, D.C., refused to air the ads. She would not comment on why they did so.

Sling TV CEO Roger Lynch, in a blog post, posited that the Peacock’s local TV stations had turned down the ad buys at the behest of NBCUniversal parent Comcast, the biggest cable company in the U.S.

“Comcast has a demonstrated history of shutting down ideas it doesn’t like or understand, predictably to its benefit and at the expense of consumers,” Lynch complained. “This is why we aggressively fought Comcast’s merger with Time Warner Cable. Our argument? That this massive conglomerate would use its incredible market power in broadband to thwart live Internet video services like Sling TV.”

In Sling TV’s “Take Back TV” spots, its first nationwide campaign that includes television ads, cable and satellite TV customer-service employees are portrayed as obnoxious children who verbally and physically abuse customers. The punk kiddies give the hapless elders no choice but to accept long-term contracts, pricey programming bundles and lousy customer service.

Sling TV execs were anticipating that NBC or other broadcasters might refuse to air the ads. For one thing, the over-the-top service’s lineup of 20-plus channels does not include broadcast content. Dish may even have been hoping the spots would be rejected so it could play up Sling TV’s positioning as fighting the pay-TV biz’s status quo.

In a similar spat, Disney and Fox refused to run ads for Verizon’s new skinnied-down FiOS Custom TV package on their TV and radio outlets. That came after both media congloms complained that the package was not authorized under existing contracts.