Because the team values its PR, since it drives ticket and merchandise sales and thereby sustains the organization, and the 'N' word in today's culture is a PR killer. You can't be a business in the public eye in today's world and let your customers' perception be that you implicitly "support" the use of the 'N' word by your employees.
The team has to act on the basis of the 'N' word alone until the matter is investigated and the details are sorted out. However, that doesn't mean the 'N' word is what caused Martin's behavior.