Can you translate this for me?
Sardony-free version:
Separate institutions mean separate rights, at least potentially. For example, if one type of domexstic partnership is called "marriage", and another type is called "civil union", then there is the potential for legally saying that, for example, two members of a marriage are next-of-kin, but not two members of a civil union. Even if they are set up the same initially, the legislature could change that down the line. On the other hand, if both types of partnerships are marriages, it becomes more difficult to make them different accidentally, and it is more obvious when done purposefully.
Your notion that the primary concern in seeking to have the same institution is whether people will look at them as normal is a typical anti-marriage formulation, seemingly designed to mask a real concern and frame the issue in a way that puts the focus on the people who are anti-marriage and how things affect them.