The main issue, missed by posters above, is that chlorinating chicken carcasses means you can get away with much lower hygiene and welfare standards for the animals whilst they are alive. .
It's not just an ill informed, knee jerk concern about human health. Many people are concerned about the wider implications, particularly the impact on animal welfare.
It's about saying no to cheaper, low welfare, chlorinated chicken from other countries in order to protect our farmers who have to work to higher welfare standards. It's also about avoiding unnecessary animal suffering.