Israel's hard right government go to extraordinary lengths to prevent Palestinian footballers from representing their national team and there are numerous other limitations imposed on Palestinian club sides in the region.
Against that backdrop, Cardiff City withdrawing from this friendly would be the wisest move as sporting boycotts can have a really big impact as part of a wider programme of sanctions against rogue states. And a rogue state is, I'm afraid, what Israel currently is under it's present extremism government.