No, it's another reason to relax gun laws. Making it easier for non-criminals to own and carry firearms would make the country a safer place.
People who intend to commit crimes with guns would think twice or scrap their plan entirely if they knew that everyone else had guns too. Nobody is going to pull a gun when they know that by doing so they'll have a hundred guns pointed at their head.
Sounds like they wouldn't have worried about it in this case, they shot up a bunch of special needs adults who would never own guns anyway.