I don't think that unrighteous behavior is funny. My statement of funny has to do with the irony of our differing views of God's actions toward humanity. One that says that unless you work for it, God won't show himself to you. And one that says that God has already shown himself to you, even though you didn't deserve his attention.

After that both of them seem to have the same expectation of righteous living. Islam as a way to prove one's self and earn Allah favor, and Christianity as a response in gratitude for God's unmerited favor which one could never be good enough to earn.