Do you have to be good Alignment to cast Holy Smite?
I ask this in the way a Neutral cleric can choose to channel positive or negative energy, It would seem that his choice would also effect this. Or is he just banned from casting Holy Smite or Unholy Blight?
No, but since the spell is subtypes as good, casting it is considered a good act. A neutral cleric who used the spell too much might find themselves changed in alignment.
So Charender are you saying that if i cast too many spells of the Lawful or Chaotic spell descriptors I'll become that alignment, is that raw or how you would rule on it?