There is nothing wrong with Presbyterians, that's my point. A Unitarian is explicitly not a Trinitarian, which is the belief position of every other church you can think of today. That is a problem if, like me, you take the Trinity seriously.
In this religion debate, I go back to this statement by TerraUnam.
It seems your problem is with the existence of Christians who don't believe in the trinity being around in the future and think, in the present, all other denominations believe in the trinity.
As a Christian who does NOT believe in the trinity, I think you are being ridiculous in thinking Unitarians are the ONLY Christians who do not believe in it. As a non-Unitarian Christian, I find the belief in a trinity to be absurd to my Biblical standards.
I found it refreshing to see a future that isn't painted where everyone is an athiest. Star Trek preaches tolerance and does not conform to any set belief in where we come from, where we are going, or the existance in an all powerful creator. It would be intolerant and even biggoted for us to presume one or no religion in this FICTIONAL future.