SFH aims to reduce what it sees as the baleful, malovelent influence over UK democracy (such as it is) and public opinion by pressuring advertisers with potential boycotts.
Peter Preston here recalls how left-wing reportage was discouraged through government encouraging advertisers to withdraw from newspapers that were critical of government 'defence' (ie, war!) policy, specifically the Suez crisis.
He develops a valid point - though once more here we can see the potential for social media and we media to have a greater impact on the poor practices of the press industry than the self-reliant IPSO.
Bullying Paperchase and the Mail’s other advertisers just hurts everyone https://www.theguardian.com/media/2017/nov/26/bullying-paperchase-other-mail-advertisers-hurts-everyone-suez?CMP=Share_AndroidApp_Blogger