I only sleeve my cards when I put them into my spellbooks. Nothing strikes more fear into your opponent than a Warlock sleeved in My little Pony Fluttershy sleeves
That wouldn't scare me at all. Seems completely normal. Contrary to popular belief, a lot of bronies ARE actually men, both physically and psychologically, rather than being physically male but secretly little girls psychologically.
Your "scare tactic" only strikes fear in people who consider their own culture's gender norms to be a fundamental law of human biology. Which they aren't. Unfortunately, the vast majority of people do believe that they are.
Source: most of my male friends in high school were bronies. All of them are more masculine than I am, and yet I was never a bronie, nor do I intend to become one.
I plan to sleeve my cards the first time I ever go to a tournament. That way I can tell my cards apart from my opponents. But... What if my opponent is using the same card sleeves as I am as well as the same mage?