If you are hiking in a place that has a lot of serious dangers, then I completely agree with your intense wording. But in most cases, for most people, if there are kids or newbies around, chill out. Try not to scare people off by calling them idiots and irresponsible.

Most scenarios in the woods aren't life threatening. Most trails a newbie or a child will be on are well established, with easy-to-follow blazes (well, at least here in the northeast, I can't vouch for anywhere else). Obviously if you have a small child, you need to know where they are, but having protocol (like them knowing that every time they get to a fork in the trail, or every time there's a good log to sit on, or something, they should stop) means being more certain someone is safe.

In my opinion, if you are taking someone who can't navigate, is too small/young to be safe, or is very new to backpacking into a dangerous hike or situation, you've made a serious mistake whether you're tied to them the whole time or whether you abandon them.