Speaking to the BBC's Newsnight, Sir Elton said companies "haven't done anything to try to stem the flow of hate on the internet".
He said a boycott could make the firms "sit up" and take action.
Sir Elton said to Newsnight's Kirsty Wark: "I don't know why they [social media firms] allow it - it's supposed to be free speech but the things that are on social media are so disgusting that there has to be action taken by the people who own these companies."
He added: "'People say 'well what about my freedom of speech?' Well, sod your freedom of speech."
He then called for a boycott, saying: "Why not? Then they'll sit up. When the money is not coming in they'll sit up.
"They can do so much good, but first they have to clean house and become a much more moral and Christian thinking... a moral thinking compass for what's going on in the world.
"At the moment they're not doing that."
*1:See also http://d.hatena.ne.jp/sumita-m/20060607/1149681079 http://d.hatena.ne.jp/sumita-m/20100322/1269285903 http://d.hatena.ne.jp/sumita-m/20100105/1262693286 http://d.hatena.ne.jp/sumita-m/20100819/1282187836 http://d.hatena.ne.jp/sumita-m/20110102/1293991362 http://d.hatena.ne.jp/sumita-m/20110316/1300247521 http://d.hatena.ne.jp/sumita-m/20110429/1304048261 http://d.hatena.ne.jp/sumita-m/20130710/1373455957 http://d.hatena.ne.jp/sumita-m/20141221/1419171398 http://d.hatena.ne.jp/sumita-m/20150316/1426473049 http://d.hatena.ne.jp/sumita-m/20150317/1426615647 http://d.hatena.ne.jp/sumita-m/20150320/1426825587 http://d.hatena.ne.jp/sumita-m/20160131/1454254511 http://d.hatena.ne.jp/sumita-m/20160205/1454683258 http://d.hatena.ne.jp/sumita-m/20160430/1461995124 http://d.hatena.ne.jp/sumita-m/20161114/1479092471 http://d.hatena.ne.jp/sumita-m/20170425/1493093730