The post you were replying to wasn't talking about moving from pro-Jewish to pro-Arab.
You can be pro-Jewish, but staunchly against what the Israeli Government is doing to Palestinian people. In fact, there are a lot of Israeli Jews who share this view as well.
I don't "support Arabs" (or Israelis for that matter) - these aren't sports teams, they're groups of human beings. Nor do I get my Israel scepticism from "drive-by social media" posts. Much of it is from simply reading what prominent Israeli politicians and their allies in western countries have said from their own mouths, on their own websites and platforms, for all to see.
I'm not obligated - morally or otherwise - to support anyone in an ethnic struggle in the middle east.
I'm not surprised by the historical propaganda. Many Palestinians don't even agree that there were Jews there before the Arabs came: https://www.youtube.com/watch?v=mkLs-yOi9gQ .