Internet Security Upgrade wants to delete Malwarebyte software

On 5/26/2013, a Norton Internet Security upgrade offer popped up on my Windows XP system.  In the process of installing the upgrade, I got an error/warning that the upgrade could not proceed until Malwarebytes v. 1.75 was uninstalled from my system.  I might have considered this except in the past 5 days, Malwarebytes Anti-Malware software actually found and removed 4 viruses that had only shown up as "intrusion attempts" via NIS.  Is this a "Microsoft-style" purge of competitors or is there really a problem.  I also noticed a small-print, check box for asking for permission to automatically feed security information back to Symantec.