Why does McAfee Endpoint Protection keep auto installing?
More than likely, you are on a corporate owned/controlled computer and they have installed the ePO (ePolicy Orchestrator) agent deployed on your machine.  This is a mangagement tool that allows your organization to ensure that end point security is installed and updated.  Additionally, it will reinstall the software if it happens to be uninstalled.

It's working as it should.

From McAfee's web page:


  The McAfee Agent is the distributed component of McAfee ePolicy Orchestrator (McAfee ePO). It downloads and enforces policies, and executes client-side tasks such as deployment and updating. The Agent also uploads events and provides additional data regarding each system’s status. It must be installed on each system in your network that you wish to manage. The agent collects and sends event information at intervals to the McAfee ePO server. It also installs and updates the endpoint products, and applies your endpoint policies. Systems cannot be managed by McAfee ePO unless the McAfee Agent is installed.


(Emphasis mine).  

Unless you have rights to remove the ePO agent, you won't be able to uninstall the software.  Even if you were able to uninstall the software or boot from a different drive to which you had rights, the ePO server would, after a predetermined amount of time, alert the admins that your machine is no longer checking in at which point they would find out what/how you circumvented the security.