Why do people even care if s get married?

People feel like it's the principal behind it, they feel like the more freedom ual get the more accepting it will become, and I honestly believe that no one is 100% straight and some people or scared that if their kids see gay people getting married that they will be fine with it and they then won't see a problem with 2 guys dating or 2 women dating. So it just ignorance they fear what they don't feel comfortable with.