This is far from the gold standard, but I find the results from surveying formerly gifted students at least somewhat compelling.

E.g., the work summarized in Chapter 3 of this:

http://www.accelerationinstitute.org/Nation_Deceived/ND_v2.pdf

Despite being accelerated reasonably aggressively, when looking back as adults, students (especially women) actually are more likely regret not being accelerated more than to regret the acceleration. On average, they report acceleration has having been very positive academically, positive emotionally, and essentially a wash socially.

It's also interesting that they are almost uniformly opposed to "de-tracking".

For advocacy, it might be more effective to give people copies of the original papers, rather than the book, depending on the audience.