I have to say that actually I think that using the word 'loser' rather than 'monster' because that's what ISIS want to be labelled is actually a very good way to respond. It being belittling as if a child who has lost a game stops them from being regarding as some sort of solider. It infantilises their cause. It removes some of their intent to create fear.
I remember Adam Hills talking about something similar and being told by security forces to do a similar thing. This is why they have often used the word 'dick' about other such incidences.
Indeed the word daesh is acronym, but it sounds like several Arabic words which carry a similar derogatory tone. One of these I believe is something akin to 'fool'.
Strangely I thought it was a good comment from Trump, and the use of language was appropriate and there is an argument that everyone should do similar.