Ah, how fun it is, especially during Advent and Christmas to attempt to mock and deny God!
Act now and get a free DVD!
Rational people will disagree that just by saying the words, "I deny the existence of the Holy Spirit" (oh no, I just said it in my head!) that it is possible to damn your soul to hell - real blasphemy against the Holy Spirit probably requires a lifetime of sin to cement. For whatever reason, I seem to recall that the Church teaches that the ultimate blasphemy against the Holy Spirit is prideful unwillingness to ask for forgiveness rather than a single utterance. Even the holiest person over the course of their life is grossly unworthy to ask for forgiveness, and we use our free will to choose what we desire, forgiveness or self-righteousness... we are unworthy of either. God doesn't prevent us from rejecting him, because how worthwhile would a slave's relationship be? We aren't slaves to God - we're either willing servants of or willing enemies with Love.
Anyway, enough blathering - back to the point:
If you don't believe in the Christian dogma, the truly rational thing to do is to go about setting straight what you think is wrong. In this case, atheists should stress their positivist/naturalist logic, because that's probably the most appealing argument you can make against the existence of God.
But that's hardly what they're doing. Things like this are born from contempt and mocking, and an immature desire to rebel against... something... God? Sure. Authority? Why not. Tradition? Hell yeah. Gotta try to fill the unhappiness with a smug YouTube video, because that'll kick ass!
They're attempting to satisfy a need to justify their rejection of God, because life genuinely without God is tiresome and empty, with no reason to look forwards or backwards - ultimately human existence is a null-sum, a simple, ongoing chemical reaction. Reduce humanity to that, and humanity becomes a false word. Without variance, atheism in all forms converges to nihilism. There can be no purpose other than animal satisfaction if we are mere animals that are self-aware by some odd neurological evolution.
Not surprisingly, RichardDawkins.net and other atheist sites are behind the success of this BlasphemyChallenge.com site. I guess all faiths require proselytizing.
The whole semi-jest perspective that most people must see this "blasphemy challenge" in brings to mind the idea that Satan is most powerful when he convinces people that he doesn't exist. Sites like this aren't really evil... they're mainly just really stupid. It is tempting to see them only as harmless fun. But they are symptoms of evil and testify to the fact that the enemy is real and is always looking for more teammates to choose his side.
And God is always pro-choice, I suppose.