Joseph,
“You should be at least as scared of his Mechallel Shabbos R”L as you are scared by that act of his.”
Who says that I am not? These are not equivalent situations. First of all, Shabbos is taught via chinuch – a child’s obligations aren’t even fully upon him until bar/bas mitzvah age, so it’s like training matches that don’t catch things on fire. And if a post bar mitzva child is mechallel Shabbos, R”L, then it’s way too late for slapping the matches out of his hand. The house is already ablaze.
“The same can be said regarding a child being mechallel Shabbos.”
No, again, see above. Shabbos is an issue of chinuch, which is a gradual process, and so Hashem built in a way to do it safely.
“A child should be as fearful of Mechallel Shabbos as he is fearful of playing with matches.”
I agree – but by the matches a parent keeps them away from the child until he is old enough to use them safely. By Shabbos our children participate from infancy. Due to that, the “fear” tactic is ineffective.
“We’re discussing older children, not two year olds.”
No, up to this point we’ve been discussing young children. Hence the running in the street and matches examples.
Why don’t you suggest limiting the parental response to playing with fire or playing on the road to that as well?”
Because a young child will not set the house on fire due to mistakes with Shabbos. And as I said above, by an older child, the damage is already done, and the goal now is a rebuild.