Is it not enough that he was a great writer?

No. His fascination with spiritualism negates everything else he's done in life.

It kinda does though. He was actively vicious about it.

As a teen, I remember first hearing about ACD's vocal obsession with "real" fairies, spirits etc. and especially the hoaxes that exploited that obsession. I was dumbfounded at the discovery that someone who wrote so many detective stories could himself be such a rube for mysticism and new age woo-woo.

That's what actually got me to go read a bunch of Sherlock Holmes, where I noticed a lot of magical thinking, correlations begetting causations, and jumping to conclusions (albeit the right ones, because Holmes is the clever hero) within his own stories. That's when I realized that yes, Doyle probably wasn't the sort of person to let reality and facts slow him down.

Arthur Conan Doyle had an original imagination, wrote adventure prose somewhere between 'very well' and 'brilliantly', and the entire English-speaking world has benefitted from his work. You jackasses, he doesn't need to have also been a titan of science or virtue (although, if I'm remembering right, he was a practising doctor). You haven't one-upped him because he believed in fairies. He was a guy who wrote vivid stories that have lasted 150 years, and his willingness to entertain kooky ideas probably contributed to his creativity.

If you want a Victorian adventure novelist to beat up on, go after Kipling like every other lazy college kid.

Spitting on an accomplished man's memory as an exercise in moral masturbation is a pretty pathetic thing to do.