Most people I encounter that flash the MMA swag either on a T-shirt, through a sticker, or in any other way, are typically fans first and have very little background in using that particular fighting style. This has risen to an almost nauseating level.
I've been taught basic defensive tactics to combat aggressive fighters that seek to bring a person to the ground within a few seconds but have few chances to commit them fluidly to muscle memory. The best thing to do is keep a safe distance to get the chance to react quickly. Just like any experienced fighter, a MMA trained fighter is dangerous and if you can't draw a weapon than you better be prepared to strike a critical area quick (temple, eyes, throat, balls, etc...).