I'll ignore the thinly-veiled racist comment and remark on the main issue at hand.
The school district's hands are tied in the matter, they have NO CHOICE but to have zero-tolerance for anything. And do you know why? That's right, kiddies.. lawyers. Regardless of what the school district does, they are under threat from lawyers. What happens if the friend of that kid who played with the 2-inch gun went home and told his/her mom that he saw a kid playing with a gun, with no other preface? That mom screams bloody murder, sues the school district for failing to protect her child, yadda yadda. The fact that it was a 2-inch toy gun at that point becomes almost moot.
We have been conditioned by the legal industry over the last 40 years that all issues are litigious. That there's no personal accountability anymore, because it's always someone else's fault, and they should PAY for your problems. Common sense took a hike a long time ago, and entities like that school district are trying to protect themselves with the only tool they have at their disposal: the complete eradiction of anything that it deems potentially violent or threatening. If innocent kids or misunderstandings get caught up in the process, then that's collateral damage that the district is willing to risk as the lesser of two evils. The fact that the mother is threatening to sue over HER child's mistreatment is yet another data point in how no-win the climate is for anyone these days.... except, of course, for the lawyers, who prey and profit off of this culture shift that they had a huge hand in creating.