If your approach is too demeaning to your opponent, it only drives them down the hole of cognitive dissonance that much further, making the situation worse, not better.
Maybe it is possible to find ways of getting the "gears" churning in the minds of creationists, while also acting "like a dick". But, it won't be nearly as easy as acting like a somewhat nice guy.
Have to do a Claus on you and say "Evidence?".
I know we all (I do anyway so that's the same as all) like to think that if we are reasonable and polite and so on that is best way to get through to someone but is that supported by evidence?