Well, I know this happens a lot in every culture there is (probably). People often are haunted their way out of a relationship by their own parents which is because of the religion of the partner of their child.
There should not be any boundaries whatsoever concerning this matter. Think about what you're doing to the (love)life of your child, you're totally making decisions for him/her that should be taken by them!
I myself am currently in a relationship with a girl who has a diffrent religion, but I'm very thankful that I am accepted in this family. I'm starting to feel more at home everyday and even that there are differences in religion or culture, it's all possible to live with eachother!
As long as there is love, it should be left alone! That's what I think