I don't think the issue is that simple. Its not making halal into haram. Its making haram into halal. ALL dead animals are haram to eat UNLESS its slaughtered in the name of Allah according to shariah. So if the people we entrust to do this does not do slaughtering in the Islamic manner, the meat 'stays' haram. Maybe we do not know it, but the meat is NOT halal. As for eating such meat or not is the decision of the Individual. But that does not make haram animal dead body into halal meat, unless slaughtered properly according to shariah.