I found another one.
I'm not going to bother to link to it, because the point isn't to single someone out, but I found another author using the phrase, "allow me to wax stereotypically" just before they said something that wouldn't be allowed in a conversation in a bar. Even when it's almost closing time and all the remaining patrons are half off their gourds. The reason why it wouldn't have been allowed is because even when people are half off their gourds, they can spot a contradiction, and after this particular author said the ugly thing he did, he contradicted himself in the very next paragraph. I'm not sure if this was an attempt to reduce the sting of the first paragraph, or to make it so people couldn't object ("Ah, but I contradict myself within the next fifty words, so you can't possibly take exception!"). Yes, readers can object even to muddled arguments. I objected so much I unsubscribed from the blog feed.
If you use a phrase like that (usually the exact wording I come across is "if I may stereotype for a moment"), what you're basically doing is allowing yourself to be a jerk for a moment, and damn what the reader thinks. By acknowledging that you're stereotyping, you're hoping you can manage a "get away with it without having to apologise" card.
Now: if the stereotype is the point of the post, or if you need to set some baseline assumptions to get your argument rolling, I can see how that can be within bounds. If you write something like, "Typical of six-year-olds, I hated broccoli," and then go on to talk about how you learned to love the vegetable, I'm cool with that.
But if the stereotype disclaimer is followed by something hideous, and then dropped and never again taken up, or if it doesn't link logically to the next paragraph — at that point, all you're doing is muck-raking. It doesn't spur people to read on. It spurs people to think, "Ick, what a jerk" and navigate to another web site.
If you're going to stereotype knowingly, please make it useful.