employer said I didn’t have enough “passion” when I couldn’t interview on a Saturday

This is the heights of unfairness! Everyone has the right to make plans on weekend and I had plans too. I specifically told the interviewer I am free for the rest of the week and when they again suggested Saturday, I couldn't attend. The employer cancelled my interview and said I didn't have enough passion because of this. What do you think of this? Is this right? Can they do this?