Christians and atheists (and, I assume, people of all other beliefs) behave in ways worse than they think they should. An atheist might eat meat despite seeing vegetarianism as the moral ideal. A Christian might cheat on a spouse despite knowing from Bible and conscience that it is wrong. Both are examples of a very normal kind of hypocrisy; all humans I know of are guilty of something they think they should not have done.
However, a Christian who freely commits acts forbidden in the Bible has reached a level of hypocrisy no atheist can reach, for an atheist (at least, so far as I know) does not declare an immutable set of moral laws. A Christian, however, has by accepting that label stated that they are taking the Bible as a moral guide.
A Christian who allows for divorce and remarriage despite the words attributed to Jesus in the Gospels on that matter is declaring that they know more about morality than their god.
A Christian who allows for homosexuality to be freely practiced despite the Bible calling it an abomination is declaring that they know more about morality than their god.
A Christian who sees any law, especially from the New Testament, as outdated and not worth following is declaring that they know more about morality than their god.
Could there be any greater hypocrisy than this? If you claim to get your morals from an all-knowing, all-powerful, perfectly loving being, but then ignore the book you claim was inspired by that being, you are espousing the height of hypocrisy.
Atheists (again, at least the ones I know) make no greater claim about the origins of morality than an evolutionary byproduct and the result of great human intellect. It is not passed down, but built up.
An atheist failing to follow rules in the Bible, seeing them as outdated due to our more evolved morality, is being entirely consistent. A Christian doing exactly the same is being entirely arrogant.
In fact, it is difficult to believe such a person is truly a Christian, for how could you disobey a being so powerful as Yahweh, or a being you claim to love so much as Jesus?
All that being said, of course, I prefer a world where the Bible is discarded as a source of morality. It’s not a very good book for that, except a very few bits which, by the way, don’t appear original. I simply don’t see any way a Christian can agree with discarding even a part of it, any more than I can see a way for Muslims to discard the Quran (although I admittedly know much less about that). There must be a great deal of cognitive dissonance there.
I know I have not pulled any punches here, but I’ll end by pointing out that, if my description fits you, this case of arrogance or hypocrisy is actually making you a better person. Keep it up!
The Complete History of the Universe: A Personal Journey 
“However, a Christian who freely commits acts forbidden in the Bible has reached a level of hypocrisy no atheist can reach, for an atheist (at least, so far as I know) does not declare an immutable set of moral laws.”
Well, objectivists should technically be atheist and they hold that there are objective morals and all that. Hence objectivism. If you read Ayn Rand’s writing, you get the sense that everything that is objectively morally good, or objectively morally beautiful, or objectively morally valuable are the things that she likes.
But when you make claims about what makes “objectively good art,” well, you’ve really lost me.
I suppose that’s fair, but then, unless that moral objectivety comes from some sort of deity, I think my point still stands.