I’m not in the camp that feels that writing fics involving real people makes you complete and utter scum. Obviously, one has to be more thoughtful when involving real people in their writing than they do working with fictional characters. At least I hope this would be obvious. However, the better fics involving real people are generally hyperbolic and involve a “what if” component.
For instance, I once saw a graphic where a person had listed their choices for a zombie apocalypse fic involving their favorite musicians. While I’m pretty sure Angus Young doesn’t have any medical training, I don’t think he’d be offended by being this writer’s choice for the medic character in their zombie apocalypse story.
I try to keep any fics involving a Real People Character component pretty gen and generally over the top ridiculous if I’m going to be making them public. Any AU involving more serious (generally metaphysical) thoughts I keep on the down-low.