As Israellycool pointed out, while desecrating a mosque is certainly not to be condoned, the words that were written, at least in the wire service photo, were not racist or inflammatory - they were Biblical verses. It is possible that there were other things written, but we have no pictures showing that.
It appears that the Palestinian Arabs have picked up on the inability of most people to read Hebrew, because Ma'an now makes a similar claim:
Israeli settlers attacked Palestinian ambulances in the West Bank village of Dier Esteyah on Wednesday, according to witnesses.The graffitum on the picture merely says "Hebron."
Red Crescent ambulances were parked in the northern West Bank city of Nablus on Wednesday when settlers wrote provocative slogans, such as "Death to Arabs" and others, according to the Red Crescent.
This is of course not proof that no settlers wrote more inflammatory things elsewhere, but it is curious that twice in a row the only pictures that we can see do not support the stories.
Ma'an reporters clearly know how to read Hebrew, so they must be considered complicit in trying to demonize "settlers" as racists or at the very least misleading readers into thinking that the graffiti here is racist.
UPDATE: Aussie Dave points out that there is a Ha'aretz video report that briefly shows the words "Mohammed pig" in Hebrew.