For your Christian friend, quote Revelations 22:11.
"He that is unjust, let him be unjust still: and he that is filthy, let him be filthy still: and he that is righteous, let him be righteous still: and he that is holy, let him be holy still."
That's not the Bible giving people permission to sin, but to tell Christians that we shouldn't force our beliefs on other people. The salvation of one's soul is between the individual and God.
As for your vegetarian friend... promise them that you won't eat a puppy if they promise to leave you alone about it.