The unreasonable morality of the athiest (Romans 2:14-16)

There is something of a schism in our atheistic friends in the way they live their lives and I've had some interesting conversations with a few of them. The part I still don't understand is how they don't follow their thoughts out to the logical conclusion.

That is... If there is no God, then man is an accident of nature. Making him not a little higher than the angels, but no better than the dirt beneath his feet. If he is no better than dirt than the highest end for man is the seeking of pleasure. Some people have this figured out and they turn to drugs. If you genuinely believe there is no God then drugs are the obvious outturn because it is my understanding there is basically no better feeling on earth than heroin.

They say its thousands of times better than sex. If man is no better than dirt you might as well enjoy a few years of sheer pleasure over 80 or 90 years of miserable striving after money or something similar. Also there is no reason for morality in the least. You are worth nothing more than dirt, thus your neighbor is worth nothing more than dirt and should you take his life there is no reason for guilt (after all it would be the same as crushing an ant or disturbing the mud).

The sheer number of people who don't believe in God doing good and having feelings of right and wrong seem to me a fulfillment of Jeremiah, "I will put my law within them, and I will write it ton their hearts." - Jeremiah 31:33b

And the truth is by living out morality in the midst of a denial of God, they are condemning themselves.

"For when Gentiles, who do not have the law, by nature do what the law requires, they are a law to themselves, even though they do not have the law. They show that the work of the law is written on their hearts, while their conscience also bears witness, and their conflicting thoughts accuse or even excuse them on that day when, according to my gospel, God judges the secrets of men by Christ Jesus." - Romans 2:14-16

And

"For his invisible attributes, namely, his eternal power and divine nature, have been clearly perceived, ever since the creation of the world, in the things that have been made. So they are without excuse." - Romans 1:20

If you're an atheist, what reason is there to pursue anything more than pleasure?