If you believe something is true, then it's true. It should be
  enough. You'd only want to convince other people that something
  is true because: a) You don't believe it yourself b) You have a
  desire for the world to experience this wonderful thing you
  experience c) You have the desire to rid the world of ignorance.
  Of course on point c) If you want to rid the world of
  ignorance.... why? Betterment of the future? Justification that
  you're right? (validation) I dunno. And even on betterment of
  the future: Do you believe there is a Utopia on Earth is
  possible? Well, that's the problem with many ideologies. We've
  never had one before. It's illogical to believe we'd ever have a
  Utopia.* Of course it's possible - and I'm all for people
  trying, reasonably. [unfortunately, I see the Utopian ideals
  with a LOT of groups of idealists - just rid the world of x, y,
  and z, and we'll all live in peace and harmony... etc etc] [oh,
  and why am I bothering to write this?* Easy.* Validation. When
  someone agrees with me, it makes me feel as if I know what I'm
  talking about, and that feels good.* When someone argues with
  me, it feels good because I said something worth arguing about.*
  And.. when people say nothing, it's because they silently agree
  or don't care or are being too polite to disagree.* All good]