From Michelle Malkin: The Dangers of Public Diversity

I am not very interested in the diversity argument, but I am interested in the standards argument. I don't really care about the ethnic or gender make up of military, paramilitary, or non military organizations. It is better to have a mix of different people and different backgrounds, if the can all meet the same standards

Selection by testing (or 'try outs') is how you get something for nothing. If you want really physically fit Police Officers their are two ways to go about it you can either train them, or only take the ones that are already fit. If you lower the standards you increase the pool of eligible people. This is not necessarily a bad thing as long as you recognize that you going to have to give them more training in order to get them to perform at the same level. The real question is: are the standards relevant. The reevaluation of standards should be an ongoing process. As a job changes so too should the requirements for the job.