How frustrating for you! Unfortunately, by emailing some specifics you armed them with something in a format they could copy and paste and share with others - which is exactly what happened.They actually demanded a list of specific critiques from me because what I had originally said was "too general" and made it seem like I was doing a drive by heckling. To me it made perfect sense, but in a little bit of confusion I acquiesced and sent a (short) list and at the end repeated that I didn't think any of that stuff really mattered, because they had teachers there to critique students specifically and the true issue was people being in professional venues before they were ready and to maybe keep them in student venues until they were. They ended up simply arguing with the list of specific critiques I sent and ignored the point completely That was my "sigh, I give up" moment.
I think I might have countered the request for specifics by raising an eyebrow and saying, "Well, since you're an experienced dancer yourself, I assume you can tell the difference between a student recital and a show featuring experienced professionals. I do think, by the way, it's great to provide students an opportunity to gain performance experience, and I hope the dancers who performed in that show appreciate what a great opportunity you gave them! I know you must have worked really hard to make it a positive experience for all of them. I'm just suggesting it might be better not to promote such a recital to the general public as if it were a professional event."