HR is required under U.S. federal and state labor laws to conduct an internal investigation, by interviewing all employees.How HR will address this is they will take the report and document it. Whether its actionable or not.
Racial slurs can be subjective, what one employee considers offensive, another might not. What's important is how the complaining witness feels, if it negatively impacts their job performance and creates a hostile work environment for them.
Hostie work environment is clearly defined in the labor laws and constitutes a cause of action.
HR doesn't make the laws, nor is it their job to interpret them. Their only job is to follow them.
A court of law will determine the egregiousness and award damages if the company is found liable and failed to take action.
The emails and other things you find annoying, are not actionable. Unless they are found to be discriminatory or racially motivated.
Talk with an attorney you could have a valid cause of action here and be awarded $$$ for it.