Dude, it's really easy to do a troubled backstory without being shit.

Say, your protagonist is a woman, black, and suffered through an abusive father.

Is he a deadbeat dad who ran away? Aw come on, that's buying into racial clichés. No, he's a successful dad who made it in life, financially, but his charm hides his violent self-loathing that he took out on her and his wife. Protagonist hero cries herself to sleep at night while her mother screams and her dad reminds her that the household depends on his money. He's a good dad in the daytime, but with the drink come the demons.

See? You just stop to think about what you're writing, ask other people, and then move into more interesting, complex territory. As a rule of thumb, have at least 3 clashing characteristics for every figure and make one of them go against the statistical majority for their "demographic". The basic criteria is that the characters need to be people, not stereotypes.

Male friend killed off to prove villain is truly evil? Reason for revenge. Female friend (or often, wife) killed off to prove villain is truly evil? You only introduced her to be murdered, you SEXIST.

This is the example where I'd agree, because "wife/daughter gets murdered as plot advancement" happens all the time. "Son/husband" is miniscule in comparison. It's a matter of evening it out. Plus, if a character is just there to be murdered, they are more of a plot device/stereotype than a person, which goes against the basic criteria. Alternative: Prove villain evil by killing off a presumed protagonist and switch protagonists. Or: Prove villain evil by brutally hurting loved one, but they fight back and escape, then have their recovery/revenge as a subplot. Both go against the grain and become more interesting.

Racial minority is physically abused? Be more sensitive to their past struggles, you RACIST.

This can very well be a part of their character. It'd just be bad if it was done in a shitty way: Racial minority is a) token sidekick with minimal backstory b) abuse conforms to a stereotyped narrative à la "Deadbeat dad was gone, so I hustled on the streets til got into fight with the po po and Louis Farrakhan turned me into an avenging badass in prison" etc.

Disabled person is unable to stop the missile launch in time? He should be able to do anything he puts his mind to, you ABLEIST.

This can work, if, again, it is not the central tension.

You're right in that white male etc. is easier to write, but that just goes to show how lazy that writing is in the first place. If you changed a character to a minority and it was racist/ableist/sexist/homophobic, your writing sucks and you should be ashamed.