I think it's up to the people involved whether to date someone outside of their religion...but I also think that, in order for the relationship to work, their beliefs need to be compatible. I dated someone who had very different beliefs from me, and while he was a great guy, we had a lot of problems because of our different beliefs, and it didn't work out. That said, I've also dated people whose beliefs were slightly different from mine, and there the difference of beliefs didn't cause any problems. There also needs to be respect for the other's beliefs.