It's been raised so I think I'll address it.
Why don't Fundamentalists follow the whole Bible?
Now usually this is asked by those in the LGBT Community who are sick and tired of being condemned by mixed fiber wearing, shaved, shellfish eating, creditcard having 'fundies' who love to cite lev 18....
These people, the fundies, clearly do not know their bible...
Ignoring for now the entire issue of what Leviticus and other old testament books of Law actually say on the matter, these are the OLD LAW.
It was written for a small population struggling to maintain its cultural identity in a hostile environment.
It is also, under the Christian faith, outdated aside from a historical point of view. Christs sacrifice changed the model from one of legalism to one of grace.
Everything is legal to me, but not everything is advantageous. Everything is legal to me, but not everything edifies. - 1 Corinthians 10:23
So why do they continue to cite Lev 18?
1. they do not know their bible as well as they insist
2. fear.... actually its mostly fear