Obviously you're able to tell a real gun from a replica at a distance while someone waving it around, but most people can't, including cops, until they have it in hand, personally. You might be comfortable risking other people's lives by making them assume that all guns are toys until they've been shot at, but people who actually do have, as a feature of their daily job, other people assaulting and trying to kill them, probably wouldn't want you armchairing on their behalf.
The solution? Actual thinking parents not sending their kid out into public to act stupid with a replica gun. To teach a kid that when they see a cop car rolling up, to perhaps consider not looking crazy and waiving said replica gun around. This is a 100% lapse on the part of parents and a completely crappy position for the cops to have been put in. I know that you would be safe, because you would omnipotent and know, from a distance, that the replica gun wasn't real, and that if it was real, the universe's special karma system would protect you from the laws of physics because you are A Better Person Than Cops Are, and bullets wouldn't be able to hurt you.