The idea is to stand up for the weaker party and that's it. It doesn't matter that Palestine is led by a terrorist group with a genocidal agenda with overwhelming popular support. They are weaker and therefore they can't be wrong, by virtue of being weaker they are automatically classified as oppressed and deserving of pity, whilst Israel being the stronger party makes it automatically the bad oppressive party in cartoon style. See also how no one doubts the obviously cooked numbers on Palestinian deaths. You can see this rationale mirrored exactly in the disproportionate criticism of Western states and specifically white settlers.