I'm not saying it's theologically sound...
But the general justification is somewhat like leasing a car. You sign up, you get your car, you make your payments for X months at Y dollars/month. Then when the lease is up you sign a new lease and get a new car. And, of course, the new lease may well have different terms.
\r\n\r\nThe Biblical version involves a covenant with God in which He gives His followers some commandments which, if followed, lead to $REWARD. Every couple thousand years they get a new one, delivered by a fresh prophet/messiah/what have you.
\r\n\r\nHence, the argument most folks will make is that Jesus brought along a shiny new covenant and everybody who became a Christian got to trade up to it, in the process getting rid of that old Mosaic clunker they'd been driving around in (which, in the theologic vocabulary, Jesus fulfilled through his sacrifice on the cross).
\r\n\r\nAgain, not saying that it hold water, just that this is the general idea behind having ham sandwiches and shrimp cocktails while still enjoying some good old-fashioned fag-hatin'; the dietary restrictions went out with the old covenant, but "kill a queer for Christ" stuck around because Jesus -- through his mouthpiece Paul -- told everybody that two guys getting it on with each other was still an abomination.
