Why did garvey consider black republicans to be the enemy?

Marcus Garvey (1887-1940) considered the black Republican politicians of New York as enemies because they published false reports against the Universal Negro Improvement Association, which Garvey had founded.  They also circulated false reports about Liberia, which was the nation in Africa where Garvey's movement hoped to resettle blacks from America.

"Fake news" is the label used in our current moment in history.  But notice that the "fake news" phenomenon has been around as long as there have been media of various kinds.

Garvey was a black separatist, who believed that integration with whites was not the solution.  The writing by Garvey that I suspect you are looking at was an editorial published in September, 1924 in "Negro World," a weekly newspaper that was published in New York.