Remember, you child will learn how to use a computer in elementary school at the appropriate developmental age.
I have to respectfully disagree with your definition of "the appropriate developmental age" in this case. My wife - who is also an elementary school teacher - and her school district see no issue in allowing children aged 3-4 to use a computer for age-appropriate activities. It allows them to follow their own interests; if the kid wants to learn about donkeys, he can learn about donkeys; and if he wants to play a matching game, he can play a matching game. There's no reason a kid that age can't do that.
If they already know how to do "everything" on a computer they will likely be bored in class while the teacher gets other children up to speed. This can cause children to become disengaged in school.
I've been using computers for 27 years, I've held job where I teach computer skills to people, and I don't know how to do "everything" on a computer. You really think a kindergartener is going to know "everything"? You should know better.
There are certain ages where things should and should not be taught and education is a very planned process of helping children learn what they should learn at the age appropriate time. It bugs me when parents push their kids to learn everything before they even enter school.
That bothers me, too. That's why we've never pushed him. He has a computer because he asked for one. He reads because he has a shelf full of books, and when he wants to read a book, he goes to the shelf and picks one out and reads it. He writes because he likes to, not because my wife and I have ever told him to. When he gets tired of writing, he puts the pencil down and goes to play with a dumptruck or a ball, or whatever strikes his mood at the time.
It sounds to me like you're trying to vilify people for doing things that you're only imagining that they're doing.
Those kids that are pushed to start reading, given math workbooks, among other things before Kindergarten are usually the ones who end up getting bored in school (and end up not being the highly successful ones) because it becomes so difficult for the teacher to engage the child. Only the best teachers are able to engage this type of child and at the same time move the rest of the class forward all while controlling behavior.
And being one of those teachers yourself, you no doubt wish there were more just like you in the school systems.
My son learned to read from watching us read to him, and from learning phonics at his preschool. Nobody has ever pushed him into reading; he enjoys doing it because he sees his parents doing it so often, and he wanted to learn; same with writing, typing, using a computer, and playing musical instruments. No, he's not as good at any of those things as we are, but nobody's bothered by that.
But just setting little Johnny down in front of a computer to bang and click to "explore" has no real merit in the educational world!
Again, you should know better than to say something like that, because it depends entirely on what the child is doing on the computer.
My son became engrossed in the planets over the summer, when his preschool introduced the kids to the subject. Ever since then, he uses Wikipedia to look up information, which he later asks me about. Because of this, he knows more about the planets and their moons than most of my wife's 5th graders. Not because anybody pushed him, but because that's what he wanted to learn. And I wasn't about to tell him that he's not at an "appropriate developmental age" to start learning that stuff.
You, like many others on this thread, seem to be hung up on the notion that if a kid has a computer that he stops reading, or playing outside, or whatever; that's simply not the case. In fact, my son uses his computer to read more than he does anything else.
And as long as that's the type of banging and clicking he's interested in, I'm sure as hell not going to stop him.