Well ... you have to do it exegetically and historically and do theology.
So lets take the mosaic commandments, from a Christian (and a Jewish) standpoint, non Jews are exempt from the mosaic Law period .... even those who worship the jewish god, unless they become proselites to Judaism they are not bound by those laws. In the 1rst Century Church there was a debate as to whether non Jews who became Christians had to follow the Law, the answer was no (except for a few that would apply universally, as well as certain principles), this is all recorded in the Pauline letters, Acts, James, and other writings in the New testament and out.
The only question comes about what if someone is a Jew that converts to Christianity, almost all Christians would argue that the mosaic Law does not apply post messiah (most Jews would also agree. the jews however don't consider Jesus to BE the messiah so they hold on to the mosaic Law), this is also biblical.
Now if someone is going to just open up the bible, pick up a verse, and say "aha you christians eat shrimp, and the bible says not to." ignoring context, intent, later explination of such verse, the Scope of such verse and the theology surrounding it, they're being stupid .... as stupid as someone going to an evolutionist and say "my grandfather aint a monkey." Sorry if you're saying that you don't know how evolution Works one bit, and People who say "ahh you christians eat shimp, you're against the bible." Don't know how biblical exegesis or theology work one bit.