The reason this has blown up so much (besides CD’s massive profile before as an advocate for horse welfare in dressage, her gold medals, and even Valegro’s visiting kids in schools) is because the whip is such a powerful emotional symbol.
When George Morris’s “indiscretions” came to light, most people knew something about them behind the scenes, but the only videos of him online were of putting thumbtacks on saddles and fat-shaming women, not hurting horses. And some of the most horrible horse crimes took place before social media and yet those people still have their “fans.” On the other hand, that woman who kicked dirt at her show horse when he dumped her was vilified, even though the horse wasn’t hurt (well, she did yank his bridle leading him out), because it was on video.
Every non-horse person “understands” whipping is bad. Hell, I am an absolute smurfy cream puff and some friends were aghast to learn I even carried a dressage whip as an aid. It’s a terrible visual image for the sport. (Which again is why I wonder why the woman picked up her camera at that moment.) A lot of my friends who very actively show dressage were even posting testimonials on their FB page that CD’s methods aren’t theirs.