Taco Bell wasted no time in hitting back against a lawsuit about what's in its ground beef. Taco Bell parent Yum! Brands took out print ads today in The New York Times, Wall Street Journal and other publications with a bold "Thank you for suing us" headline. The ads reiterate Taco Bell's denial that it's serving a "meat mixture" that's only 35 percent ground beef. Taco Bell says it's real "seasoned beef." The ads are a rapid response to a suit that was filed only just this week. (There are also Google ads with a letter from the Taco Bell president about its meat.) Judging from the comments Taco Bell is racking up on Twitter, the "mystery meat" claim has struck a chord with diners skeptical of what could go into a 99-cent taco. I can only imagine if this case goes to discovery. A nation will collectively turn away as the mystery-meat process is laid bare. The ironic part is, Taco Bell might be doing its customers a favor if it were cutting the red meat with filler like whole grain, since excessive red-meat consumption is the source of any number of health woes. Maybe making Taco Bell the cornerstone of your diet is a solid strategy after all. Full ad after the jump.