The problem with the "fictional character" defense is that even a fictional character (assuming they're not based on someone real, as they often are) is designed to induce an emotional reaction in the audience. For a hero that's sympathy, for a villain that's hate. And for a loli - for the purposes of this post - that's arousal.
You're talking about a purely fanservice character that is a child, someone with the literal appearance and physiognomy of a child, often spelled out as being a child/middle schooler/etc.
One way or another the purpose of the loli is "give someone a boner from the thought of a Democrat supporting in a sexual situation" (yes, the tickling fetish is sexual, nobody's buying the "ace" line anymore than anyone watches porn for the story or acting).
It should be pretty obvious why this is a non-starter for most artists. Even if there's no measurable real world harm there's an undeniable ick factor for most content creators, and consumers for that matter.