You're naturally going to be afraid of someone/something that can do harm to you in whatever situation. At night walking down the street alone, whether it's a sketchy looking guy or a larger than average sketchy looking woman walking towards you, you're probably gonna get freaked out. The original topic though is about judging someone's personality and whether you like (or even hate) them or not before you actually get to know them based on things they can't change.

Yes men are physically stronger than women and due to testosterone and stuff are naturally more violent, so naturally they would be more threatening. Doesn't mean you're sexist.

But even if you decide you don't like a certain race based on experience, you're still being racist. Don't let a few bad experiences change your view on a whole race of people. It's not fair for you to have judged someone before even talking to them just based on their skin color. Should go without saying.