Most of the posters are racist if "donkey" is a racist term. I have just searched "donkey" here and got many results (e.g. Antonio, Kamara, Ings, Maguire, Martial, Rashford, Shaw, Carroll, Duncan Ferguson, Firmino... I have no time to list all of the players who were called "donkey" just in the last few days). The "voodoo" is a bit different, but that's part of Lukaku's story and I think Zlatan made a reference there. So I think that his intention is not racist, but these days you have to check the colour of the people and think through what to say, because you might be easily interpreted as racist (e.g. "donkey" seems to be racist for some odd reason).