In a large community, marrying out is a personal decision that a family either accepts or does not. In a very small one it carries an extra weight, and pretending otherwise makes the conversation harder.
What the reaction is actually about
Rarely the person. Usually one of these:
The community getting smaller. Every marriage outside is felt, by the generation that remembers when there were far more households, as one fewer family. That is not bigotry, it is grief, and it is worth recognising as such.
Whether the traditions survive. Christmas, the food, the church, the name. Parents picture grandchildren who know none of it.
Whether you will still be part of it. Families worry that the couple will drift into the other family's world, because they have watched it happen.
What helps
Say what you intend to keep. Not in general terms — specifically. Christmas at home. The church. Teaching the children to make kul kuls. Whatever it is, name it. Parents relax enormously when they hear that the things they are worried about losing are things you have thought about.
Let them meet early. The objection lives in the abstract and rarely survives meeting a warm, ordinary family.
Don't argue about the community's future. You will not win it and it is not really the subject. Acknowledge it, then talk about what you will actually do.
If you are the parent
The most useful thing you can do is separate the two feelings.
Sadness about a shrinking community is legitimate and worth saying aloud. Refusing a person because of it is a different act, and one that families frequently regret for a long time.
Say the first. Do not do the second.
What usually happens
Most families come round, and the ones who do usually say afterwards that meeting the person was the turning point.
The families who do not tend to be the ones where the news arrived as a settled decision, late, with no role for anybody else.
The conversation goes better when both sides admit what it is really about. It is rarely about the person, and pretending it is guarantees an argument that solves nothing.