this implies that wronging a fictional character is a severe moral issue

for that reason I agree that depicting a child who really exists should be bannable (e.g. drawing some kid you saw irl) but if it's drawn and viewed by adults and depicts a fictional character then there are no children actually involved, so I don't think it's particularly immoral

sure but it's still a drawing
unless you think there's a threshold which turns a fantasy into a crime itself that shouldn't matter
porn with gore is also all over but the people who make and view it probably aren't all serial killers

yes but that's thought crime
weird drawings of that nature are no worse than drawings of rape or snuff or anything like that
no one's investigating rape fantasy artists for criminal activity