Kids are, by their very nature, different from adults and thus your implied argument that it's the same as pre-judging another adult (I assume that's what you meant by "person) doesn't hold water.
I disagree, that for the purposes of dining out, a child that can meet the standard of adult behavior is different from an adult.
The bolded also doesn't make much sense, because I've always held to the idea that just because something isn't prohibited, doesn't mean it's a good idea. Should we not be annoyed when parents fail to recognize clear contextual clues about what is and isn't kid-friendly? Do restaurants really have to say "No children after 7pm" or "No children, period" for you to know that a pricey steakhouse famed for romantic dates and imaginative cocktails is not a suitable place to bring your 8yo for a late Saturday dinner?
It depends on the restaurant. Using your scenario, I wouldn't take a child, no. But many of the examples being given are not so clear cut.
A high end steak house, not billed as a romantic spot? Sure, my son loves steak.
An expensive restaurant that doesn't have kids menus? Sure, I've never understood the kid menu thing and my kids didn't use them much.
A bar? No, bars 21 and over only.
A pub? Sure, most pubs around here don't go adult only until after dinner.
A museum? Without a doubt.
Backpacking? My kids have been backpacking since they were in elementary school and could outlast many adults.
A rated R move? Well, I wouldn't, but I don't see a problem with it if the kid can handle it.
A nude beach? Not my thing, but there's a nudist resort in the next county over and, from what I hear, they're very family friendly. So, if that's the way you're raising your kids...
My point is not that there aren't places kids shouldn't be taken, there are, and I said so in my first post. My point is that the behaviors people seem to be objecting to are just that, behaviors. It's not the kid's presence, it's the behavior that matters. Not all kids are misbehaved and many kids can be counted on to behave well in the situation in which their parents put them. And I don't understand the idea of objecting to the mere presence of a child. The example above of the 3-year-old going around to tables introducing herself is an example of a child that shouldn't be taken to *any* restaurant. Not because she's a child, but because her parents seem to be encouraging her intrusive behavior. I wouldn't want that at a burger joint.