Am going to go against the grain here to say that 'child abuse imagery' is actually a sanitised term. 'Child porn' is the stronger term because when you say that a man has been caught downloading child porn, everyone knows what men do with porn - they masturbate to it. Whereas a man caught 'viewing child abuse imagery' sounds very passive; the specific sexual purpose of it is elided - after all, anyone could 'view' child abuse imagery for any number of purposes, including legitimate ones, such as law enforcement officers reviewing material for a case against child pornographers.
Further, images of child abuse also include things that aren't sexual in nature, such as photos of a child's bruises in a police file. And 'imagery' obscures the fact that people produce these images for a specific purpose, i.e., masturbation material for paedophiles, whereas 'porn' draws attention to that fact.
Of course, everyone 'knows' for what purpose men are downloading child porn; I'm not claiming that the use of 'child abuse imagery' means people will actually be ignorant of the fact that paedophiles are seeking this material in order to masturbate to it, what I'm saying is that using sanitised phrases to describe it actually distances us from the full, ugly horror of what's going on: that there are people, overwhelmingly men, who are sexually excited by watching children being raped and tortured.
In my line of work we use the term 'indecent images of children'.
An even more sanitised phrase. Think of the visceral response 'child porn' induces vs the polite, almost prim 'indecent images of children'. That's part of the reason people prefer these sanitised phrases that implicitly elide the fact that this material is produced as a masturbatory aid. It's less viscerally upsetting, creates emotional distance.
Am fully prepared for most people on this thread to disagree with me.