She said, “Ugh. Losers. I get like ten of these a day,” and clicked [delete] on all of them, without replying."
While his thesis might be true, this is not a good example of it.
Those guys undoubtedly sent off many such heartfelt messages each day. They're playing the law of averages, and their chances are much better if they indicate they read her profile.
And like she said, she gets 10 of those messages everyday, so she can afford to be choosy. If she answered every one of them back, they would all e-mail her back, and get their hopes up, and she'd have to e-mail back... It's a waste of her time to bother.
It's not callous, it's a reflection of the reality that men are much easier than women, making women a comparatively rare commodity.
This happens in real life all the time, and the only thing that's different online is that men can send such messages without having to overcome their shyness. So women get many more messages, and have to be comparatively more selective with them.