In many ways I'm shock there is Google Results about why rainbow dash is gay. The reason because for a character that loyal to her friends, tomboy, lover of sports, action, speed. I don't really want cover those theory's or that video on YouTube Proofing Rainbow Dash is a lesbian. Mainly the reason does not make any sense. Based on Rainbow Dash is a character mainly focus more about the following stuff: her friends, being a tomboy, lover of sports, action, speed.
Some people would think gives ideas to sharp the character but the honest truth much better for the character stay in her friends, being a tomboy, lover of sports, action, speed and the reason because more fitting, staying in text of the character.