Not hard to answer that question. The Muslims have made life miserable for them. Abbas isn't Christian, no members of the PA are. He makes this annual spectacle of himself to simply get tourist dollars, nothing else. The rest of the year he treats Christians like second class citizens.
Abbas has stated dozens of times that his 'Palestine' will have no Jews in it. That goes for Christians as well.
Don't be fooled by Abbas in his holiday mask.