Although this article doesn't give the school's rationale for nearly suspending a boy for bringing in Lego gun, on the surface it sounds like the perfect argument against Zero Tolerance. It's a non-issue, because the kid didn't actually end up facing any disciplinary actions (as far as we know), but in this day in age, that's more like saying the kid got lucky.
It takes a leap of faith to believe anyone would lack so much common sense as to go as far as suspending the kid over simply bringing the two-inch toy in... now if he was going around pointing it at other students and saying "bang you're dead" or something, then we'd have some reason to go on, but this article seems to go out of its way to present him as a typical kid who became a victim of circumstances, and I have no doubts that he's anything but.
In any likelihood, the parents are probably even more to blame for bringing this to the attention of the press over this momentary lack of common sense on the school's part. It seems to have been quickly corrected. Who's really making this an issue here? And if you still believe sanity exists in this world, you could argue that maybe he was causing such a disturbance that such a move was necessary for another reason entirely, but that would take some faith in the sanity of Zero Tolerance.
All I can say is, suspending and expelling all the little Lego gun carriers in the country isn't going to stop school shooters.