I actually think you're giving Mr Trump too much credit in choosing to describe ISIS the way he did. The President has previously explained he sees the world in terms of 'winners' and 'losers'. i.e he's a 'winner', Putin is a 'winner', Freedom Caucus has 'forgotten how to win', Democratic Party are 'losers', people that vote for him are 'tired of losing', etc
Unlike George W. Bush (who saw the world in terms of 'good' and 'evil'), Mr Trump doesn't measure people by the principles underlying their intent, but solely by the effectiveness of their execution (hence his admiration for Putin, KJU and other strong arm dictators). In this sense by calling ISIS 'losers' he was not making a heartfelt condemnation of the Manchester attack, but rather a critique of the organization's efficacy in achieving its desired ends
