[annalex]

Indeed, one should never pray Hail Mary, or any other prayer vainly, without understanding it.

[NoGrayZone]

You should have just let it be.

[Mad Dawg]

Neither should one pray it thinking that he may be heard for his many repetitions.

And in related news, when an anti-Catholic cites a text in an argument against a Catholic practice, he probably and usually ought to read and consider the whole text. And before arguing against all repetitions he probably ought to read psalm 136, "For His mercy endures forever."