There will be ingame Voice chat, so that is kinda not really useful. 
Though dedicated custom gestures could contain Audio. Ofcourse only if the Server allows for those. In a LAN Game (which technically is a Server but with different Defaults), you can honestly just trust people with their content, since they are usually in the same Building as you.
Not to mention people manage to make offensive MC Skins, and you know how limited those are. If someone wants to make something offensive they will manage to somehow do it.