I don't see why it's a big deal. So, someone thinks this, that or the other thing is a quack. It might be interesting to discover why. Sometimes there's a good story there. In the end, it's still just an opinion.
Now, if someone said my daughter was a quack, them's fighting words. Unless, of course, she's selling snake oil. Then I'd just quack at them and send her to a trade school or something.
As far as this specialty goes, bad stories travel faster than good ones. Also the widespread impression of seeking lifelong appointments might leave people thinking the whole lot of them are charlatans.
Just share your positive story. It'll stick in their heads and maybe they'll share it the next time chiropractors come up in conversation. And, they do come up. Especially if you've ever had jury duty. Oh, that might be adding to the bad reputation as well. The whiplash as a winning lottery ticket reputation.
I had massage therapy for many months after a botched surgery. It was painful and I don't think anything positive came of it. Yet I don't walk around condemning massage therapists. I'm sure many people enjoy and appreciate them.
Just my take. I'd rather hear people's stories, positive and negative, than get my dander up over someone's opinion. So, let's all hug and go eat some cheesecake.