"Hard not to point out difference in the way antisemitism cases have been handled," Mr Campbell tweeted. "Plenty of precedent of members voting for other parties/causes. Some are now senior party staff."
MP Jess Phillips said Mr Campbell was expelled quicker than a man in her local party who "denied the Holocaust", adding this man remained merely suspended.
Some also pointed out Jeremy Corbyn had approvingly noted George Galloway's victory when he caused a major upset by defeating a Labour candidate to win Bradford West in 2012 - but faced no action by the party.
Emily Benn, who stood for the party in 2015, pointed out that Andy Fisher, who is now a senior aide to Mr Corbyn, publicly urged people to back her Class War opponent rather than vote Labour in her Croydon South constituency.
Comedian Matt Lucas wrote simply: "Dear Labour, that was quick. Yours, a Jew."
