I agree with you on not being so offended, because yes, Sherlock was treating the student differently, it's even mentioned in this short fic in the beginning. I also realize the author was writing about the world as he knew it 100 years ago, and for me, historical fiction is successful when it's not stating 'this is why they were all wrong back then.'
Re: spoilers for The Three Students, although it doesn't really matter if you've read the rec :)