I don’t know whether Comcast has a strong case in its suit yesterday charging that DirecTV is misleading consumers by advertising “free” access to its NFL Sunday Ticket service. But the filing at the U.S. District Court in Chicago shows that the No. 1 cable company sure feels passionately about the matter. “This is a false advertising case against a serial false advertiser,” the complaint begins. DirecTV isn’t offering the football programming for free, Comcast says: ”Only in a maze of dense disclaimers and sub-disclaimers, DIRECTV discloses that the offer (i) applies only to new customers, (ii) requires a two-year commitment, (iii) requires enrollment in a premium level of service, (iv) applies only to 2011, and (v) entails automatic renewal in 2012 at ‘special’ renewal rates.” Comcast wants the court to stop DirecTV’s ad campaign: “Given its history of relentless false advertising, DIRECTV likely will attempt to stall until the NFL season is well underway, and consumers have been duly misled, before withdrawing its current campaign. Unless the Court takes immediate action, DIRECTV will be emboldened with the belief that it has the right to lie with impunity and avoid liability for its deceptions.”

Comcast says the DirecTV ads violate federal laws prohibiting false advertising, Illinois’ Consumer Fraud and Deceptive Practices Act, the state’s Uniform Deceptive Trade Practices Act, and common law barring unfair competition. The cable company wants DirecTV to retract the ads — and pay Comcast “all profits wrongfully derived” as well as triple the cost of damages, and a punitive fine to go to a consumer protection agency or advocacy group.