Rockstar has stated in a blog post that they will not ban people for using Singleplayer mods and that even though they like seeing them they are still not authorized by their EULA. So anyone banned by Rockstar might want to ask support and tell them why they should be unbanned or tell them at least what they were doing.
But neverless they have officially approved single player mods for GTA V as being okay to use and you won’t get banned by them.
Source: RockstarGames Blog