Secular humanism does not, in any way, suggest that life is totally meaningless. The no divine purpose, absolutely.
I have never met a secular humanist angry at the notion of answering to a higher power. Typically because the whole concept of a higher power is anathema to them. Why would they be angry at something they don’t believe in?
I, an admitted agnostic, would not cringe at the idea of such an audit as you suggest. I am not perfect, but I don’t shrink from my actions, as I have tried, and continue to try, to live by that very simple, golden, rule. I am no more or less a sinner than you are (as Christians believe we are all sinners, right?), should I be proven wrong and stand before the pearly gates.
Arrogance comes in all shapes and sizes. You exhibit plenty, given your second paragraph (anyone capable of rational thought - as though you have a monopoly on rational thought).
I figure that it’s a great big world out there, and I’m OK with the idea that we can believe different things. I have no need to proselytize you to my way of thinking, and frankly, I would not be terribly open to your proselytizing, either.
I believe the standard reply to that from the viewpoint of mainstream Protestant theology would be that while you're both sinners, the Christian has been forgiven of his sins and will go to heaven.
As opposed to you, who will burn in Hell.
I recall reading "The Great Divorce" by C. S. Lewis in which someone who has died and gone to Hell gets to visit the outskirts of heaven (some sort of work-release program, presumably). He meets someone he knew on Earth who committed murder and was executed. He's rather upset by this, saying something to the effect of, "He gets into heaven and I don't?" It turns out that the murderer was genuinely repentant before his execution and accepted Christ as his savior...thus he gets to go to Paradise, as opposed the the main character who (while a nice guy) wasn't a Christian.