Sick and twisted either way, and all the moreso if drawn for adult consumption. Pretty sure in the US even drawing kids doing that is against the law and the author would no doubt be enjoying getting his fudge packed courtesy of the feds.
It is illegal if you can show that they are kids or likely to be mistaken as kids. Nobody is getting arrested for it. Prosecutorial and investigative resources have more than they can handle with real children being exploited. I think you'd have a pretty tough time proving beyond a reasonable doubt any of those drawings are of children, anyway. I work Homicide and even I get ick-ed out talking to the Crimes Against Children detectives. I would have had a very short career working in that office, hats off to those who can do it.
But, yes, it's offensive and that's the point. Same as the "artist" who put a crucifix in urine decades ago and got a ton of press for it. It has exactly as much power as you give it, if people didn't need their little boost of dopamine from being outraged and ignored it then he would still be some nobody failed artist. Same here.