I can speculate on a couple of possibilities..... 1) Some folks are afraid of those who are....."different". This is expressed in all sorts of ways, most of them ending in -ism. 2) Some folks were taught, or learned, that the universe works a certain way, and they accepted it completely. So when something challenges that mindset, they feel threatened - even when the challenge doesn't affect them in any way. 3) In recent times, it has become possible for same-sex couples to get married. Here in the USA, "straight" folks have a marriage success rate of 50 to 60 percent - and it's been that way for over 50 years. What if - just SUPPOSE - same-sex couples wind up having a higher marriage success rate? Not saying they will - it's way too soon too tell, and the sample size is way too small - but - just SUPPOSE that they do? And then "straight" folks would be asking them "what's the secret?"