Quick explanation: see post above by TJ, that pretty much nails it.
Perhaps they did not realise that a username of 'familyshooting' might generate the wrong impression. In that case, problems will follow them everywhere. Some will be OK with such a name and realise what it might refer to, others will be shocked. Here, we have to play safe, and gently ask people to try not to cause offense. If someone can't see what the basic problem is, then they are not suited for here, and that's all there is to it.
Plus it may have been a business name in any case, so it's a double-no here.