The occupation of Haiti is necessary because if that land mass isn't occupied, then there is even less space for everyone else in the world. Does Haiti need to be so heavily populated? That's not really for anyone to say. That place is where those people grew up and where their parents grew up. It's part of their way of life.
Haiti is in such bad shape that it might need to be occupied by a competent government to help get the island out of trouble. The small island has been in terrible shape for many decades because of different corrupt leader and the people of the island are not willing to improve.
Woodrow Wilsons occupation of Haiti was a necessary action he had to take to protect American business interests in the area, the occupation was short lived but it sent a strong message to Haiti's Government that foreign business interests in Haiti must be treated fairly and be safely protected, so I do believe it was necessary.
Assuming that the word occupation here refers to a military occupation (and not asking is it necessary for anyone to live in Haiti), the answer is no. Haiti is a poor country and it is still recovering from a national disaster. That does not justify sending a foreign occupying force to create hate and discontent with the local population. Financial aid and material assistance is more likely to help Haiti then occupation. What they truly need is a plan for dealing with their own corrupt officials, but occupation won't solve that, either.
I do not see anything necessary about the occupation of Haiti. They do not pose a threat to the international community. And I think that any problems that Haiti and its citizens are experiencing should be left for the country themselves to take care of. I do not think there is any benefit to occupying Haiti.