Recommending the use of a software for a purpose it wasn't meant or designed for, is the real bad argument. There are a lot of projects that use forums for support questions just fine. Instead when you offer a chat room, people will try to get away with quick answers. But it rarely ends up like that and all the conversation that ensues also becomes buried.

Short lesson - use software for what it's meant for. Don't shoehorn a support forum's job to a chat application simply because people already use it.