I believe the answer is: It viewed European interference in the Americas as a threat to US national interests.
It helped colonies in North and South America adopt a democratic form of government.
The monroe doctrine view European interference in America as a form of manifestation of an unfriendly disposition toward the United States.
He believed that all the 'help' that the European give is a camouflage for their true intention, which is wakening United States' government from the position of Ally and slowly taking over control and replace our democracy.