As travel becomes easier and local communities across the world become increasingly diverse, the chances of marriages between people of different religions also increases. In the US alone, interfaith marriages have increased from 20% in 1950 to 45% today. For people in such marriages seeking common ground, values matter more than beliefs.
This poses a threat to religion because while being married to a person of a different faith does not mean that one gives it up, it does weaken the ties to religious institutions and, more importantly, reduces the chances of children being indoctrinated with just one faith and thus thinking that it must be true.
The important thing is that people be weaned away from institutionalized religions and, most importantly, their allegiance to holy books. It is the latter that leads to dogmatism and intolerance. When people are just generally religious and/or spiritual, they have to figure out their values and morals on their own and are far more likely to come up with a good set than the ones they supposedly get from the holy books.