For many people, discrimination does not exist on a scale of 1 to 10. Rather, it's either a 0 or a 10, with no in-between. You're either enslaved, lynched, have laws against you, etc. or it's just not discrimination.
These people are inadvertently admitting they wouldn't do much to stop things like racism, if it weren't for the history behind it. Basically, they would ignore or even partake in racism, if racism had no history of slavery or murder or corrupt laws. They would ignore wage gaps, insulting stereotypes, negative media portrayals, eugenics, and general everyday animosity because "it could always be worse."
This black and white mentality is called the fallacy of relative privation (read more here).
Funnily enough, whenever these people have an issue, all of a sudden they don't compare themselves to others who have it worse. Many still bitch and moan when they have a splinter in their nail, in spite of people with arms or legs ripped off. They will splutter and cry in pain if you beat them bare-handed, despite people out there getting stabbed or shot.
We could go on and on with this. People get mad when their restaurant order has a hair in it, without thinking about all those starving orphans who couldn't care less. People get depressed or angry when they're cheated on or dumped, when there are others so disfigured they will likely never have a relationship in the first place. Depression and other mental health issues are taken seriously in modern society, when there are people living in war zones right now.
Speaking of mental health, I do find it funny how society takes this seriously until height is brought into the suicide discussion. Then nothing matters unless you're enslaved or killed first.
This whole thing is just a convenient excuse to dismiss any problem... At least until something is their problem.