It is the worst case of mistaken identity, Haitian looking guy found in Haitian puta area with a knife in the pocket (a bit well off looking, with a pasola + knife = could be a dangerous Haitian pimp !?). I think if you had some kind of ID on you, it would have been very useful.
The PN guys found you an easy target, they do the same to Haitian guys every day, so didn't think of it for a minute. But now for not loosing face they just don't come down and admit their mistake - because that is not easy and also could cause bigger problem for them, hence the ongoing saga.
To be honest, I say you tried and tried really well, but police here is corrupt really bad, they get away with murder (local or foreign) so your case really fade in significance - police mistook you for a Haitian and took your KNIFE and some money (ok, threatened you, no harm was really done - could have broken a few bones and it was still way of the chart, comparing to murdering people here everyday for nothing... ! You found a case yourself).
If you plan to stay, kiss and make up as someone suggested. If not, lay low for a bit until you can leave. Not sure what would have happened if you have not complained, but these are really the options now. The PN guys would not be punished, they might have got verbal from a ranking officer to watch the f**k out when shaking off Haitians - make sure they are not gringos !?
I think in future, considering your appearance (I know, unfortunately that is the world we live in), have a colour copy of your passport handy, and pull it out right away before even saying Hola to anyone - oh, and the most important thing from my point of view, don't carry KNIFE or other weapons, the police (in any country) get really worried when they see weapons, they would think this Haitian guy could have pulled it out and stabbed them with it !?
(sorry for the lecture, didn't mean it that way).