[doty]

To pile on the pedantry: "data" is one of those words that can be used in either a singular or plural construction. The OED has references going as far back as this one, from 1807:

W. IRVING Salmag. xviii. 366 My grandfather..took a data from his own excellent heart.

(Further proof that English is not Latin.)

[dhimes]

I agree that it's a tough game to standardize usage, especially when different "experts" don't agree (I would guess that you could find writing by other authors circa 1807 that used "data" as a plural). Currently, you find the use of "gender" confused with the use of "sex." Over time "gender" will probably come be used generally for male/female, and sex for reproductive references. But the first such uses were non-standard.

Perhaps it's best to leave it at, "know your audience."