I think that the "antihaitianismo" here is a way to hold the border, to secure cheap labor, and to maintain a nation identity in the same way as the denigration of Mexicans in the US as "wetbacks", etc. is and was an effort to maintain the US border against an influx from the poorer nation into the richer one.
And maybe 'antihaitianismo' is functional in maintaining mental health? If people define it as a nationalistic issue rather than a race issue then they can avoid any chronic alienation by remaining largely indifferent to state negrophobia?