Because they took an oath to defend the Constitution. That explains Paul's support.
Obama? Beats me. I guess theres' an irrational, emotionally dominated component in every population.
BZZZZTTTT!
I took an oath to defend the Constitution and wouldn't trust Paul with any office higher than dog catcher (I used to like him as a congressman, but no more).
So if I suddenly supported Ron Paul, it would be explained by sudden brain damage. Or by someone usurping my name and former occupation on a donation card.