Originally, the Latin word for "left," "sinister" didn't have any connotations for good or bad, but in the Classical era, it started to take on associations with misfortune, awkwardness, and evil. (Other societies throughout history have done the same sort of thing, but not all--the left hand has also been linked with wisdom, skill, magic, healing, and divinity.) So much superstition!
Growing up as a lefty, I clearly remember an older elementary school teacher deriding me, saying, "you write like a cripple" as she observed me. It was the mid/late '70s, and I remember telling myself that she was speaking from an old-fashioned bias that I should shrug off, but I also knew how incredibly rude it was. She managed to insult both me and kids with genuine physical disabilities/handicaps in one fell swoop, too.
My dad, born in Brooklyn in 1930, was left-handed all his life, and though I don't know for sure, I imagine he faced much, much worse for years. I'm grateful that I grew up in a time and a place that was more accepting.