Israel and a few countries who have hostilities often refuse to shake hands for many reasons...protest, political, ideological. It is considered poor sportsmanship but it's handled case by case, by the governing bodies of each sport. They can be disqualified, sanctioned, or given a pass, depending on situations/officials. It's not terribly new.
I said Israel and a few countries have hostilities, I guess I worded it badly as to who refused. It doesn't really matter though, the point is still the same. Athletes can and do make political statements and it's not new, and they get dealt with on a case by case basis.
If you know anything of the Palestine Conflict, you'd pretty much understand his (El Shahabi) attitude. Although, it's the farkin' Olympics, create peace man!!
I don't give a rat's ass about the Palestinian struggle/conflict/irritation. Neither one of these competitors were involved. The Olympics isn't just about who's the best; its about epitomizing what sportsmanship is all about. If you cannot be sporting, you don't belong at the Olympics. Full stop.
Btw, they sent the impolite fuck home:
http://edition.cnn.com/2016/08/16/sport/israel-egypt-judo-handshake/