I think the ability to debate pseudonymously is very important. But I think it's also totally reasonable to do so under your real identity, if you feel comfortable. Lots of people blog, for example. In many ways, Facebook serves much the same purpose as a blog to me, but with better discourse.

Also, real identity carries weight in a discussion because you're socially accountable for your views and conduct. Now, again, I'm privileged to hold views that are socially, politically, and professionally acceptable in the spaces I inhabit,even if they're not often fully shared. But I also don't think that's coincidental.