It's a good assumption to make if someone points out a random person on the street and asks you to guess their sexual orientation. But in an article about male

It's a good assumption to make if someone points out a random person on the street and asks you to guess their sexual orientation. But in an article about male and female relationships and sexual attraction? It's a pretty bad sign that the author just assumes heterosexuality for everyone, especially when anything else would defeat (or at least greatly complicate) their argument.