Excerpt from Oral Argument:

“When a employer fires a male employee for dating men but does not fire female employees who date men, he violates Title VII. The employer has, in the words of Section 703(a), discriminated against the man because he treats that man worse than women who want to do the same thing. And that discrimination is because of sex, again in the words of Section 703(a), because the adverse employment action is based on the male employee's failure to conform to a particular expectation about how men should behave; namely, that men should be attracted only to women and not to men.”