Really, people? Really?
Let me tell you a story about Starbuck and Boomer from Battlestar Galactica, who were both men in the original series until the re-imagined series decided to make both of the women. Oh, you betcha there was outrage from fans of the original, seething and raging and sending hatemail because how dare they make iconic male characters into women! This is a disgrace to the original! But then the mini-series for the newer Battlestar Galactica aired and suddenly everyone shut up with their hate and anger (except for a few, including Dirk Benedict himself, where he sees a woman Starbuck as "emasculating" the role altogether and that is a deeply problematic mindset to have.) But the new BSG thrived and now, Kara "Starbuck" Thrace and Sharon "Boomer" Valerii are considered to be iconic and empowering in their own way, and rightfully so. Granted this was due to how groundbreaking RDM's Battlestar Galactica was in general, by them pushing beyond the boundaries and making political statements about gender equality, and it was their intentional to change the genders of Starbuck and Boomer and add another layer on the many layers they had for the show that the original series didn't have.
Aside from that, we have the case of Kono from Hawaii Five-0, who in the original series was a man before the reboot changed the character to be a woman (and ironically, Grace Park plays both Kono and Boomer, lol). And let's not forget Warehouse 13, where they made H.G. Wells (you know the famous English male author) into a woman.
We don't know if Elementary is making the conscious decision in being progressive in this sense, which I highly doubt they are, but by suggesting that you can't genderswap characters all because you think it would disgrace the original source is plain ridiculous. Genderbending is not impossible and can work, as it has been proven by the examples above. If this bothers you so much, well, then that's your own damn problem.
People are being so ridiculous and outrageous with this, I can't even. Everyone just needs to take a step back and chill the fuck out. It's getting way out of control from both sides at this point, far beyond mere just stating your opinion, and I'm kind of tired of hearing about it, tbh. And yeah, I kinda got a little worked up over what this one person said, but it's reflective on a common (and problematic) mindset and it really just struck a cord in me that I needed to let it out.