I tend to agree. Since GA Real Time updates every few seconds, your server would have to pull that information and display it. That might eat up your server resources. (I also may have no idea what I'm talking about. You make the decision.)
The question is, who all NEEDS to know that information? How will the forum membership be better off having it displayed?
I, personally, don't think it will. It's kind of like the old counters that 'webmasters' used to put at the bottom of their websites. Now it's just taboo.