If a company has a diversity policy,like discrimination and there were employees who complained about this facet of the policy, what would you do?

Employee related problems and opportunities, HR manula can help you to take decision. There are many supllementary policy as Complaint Response Mechanism, Anti Bribery & Anti corruption policy, Sexual harressment policy, Fraud policy as well. When you take any decision, keep mind of every policy, otherwise decision will not be appropriate.