Floyd Landis ignored desperate pleas from his sponsor to avoid a public fight with Lance Armstrong, according to e-mails the seven-time Tour de France champion released in trying to prove the disgraced cyclist has "zero credibility." Armstrong released the messages Friday in a second day of attacks on Landis, who accused cycling's biggest star of doping, teaching other riders to cheat and paying off a top cycling official after allegedly testing positive in 2002. Armstrong has denied those allegations. "Even a superficial review reveals a troubling, angry and misplaced effort at retribution by Landis for his perceived slights," said a statement posted on Armstrong's RadioShack team website.