I'll shine some light on this. It's not unique to liberals though. It's seen on both sides.
There's a certain mindset involved where people who are aware of misdeeds committed in the past, but didn't have a
direct connection to them wind up feeling responsible. Usually, this is because of ingrained things taught when an individual is still very young, and has parents or guardians who rely on personal shaming and reinforced guilt (wherein a child suspected of wrongdoing is "wrong" by default automatically, and essentially guilty until proven innocent) as a disciplinary feature. This fosters someone viewing their own accomplishments in a negative, often making them wind up unable to see their own abilities because they have had it enforced for some time that they are deeply flawed and thus automatically responsible for everything wrong in the world due to their own parents/guardians using automatic guilt and blame-and-shame. This eventually results in a situation where someone feels guilty even if they did nothing wrong. All it takes is a minor even tangential link, and the subject feels genuinely responsible.
"You're automatically wrong, so shut the fuck up."
You can see, given this, the obvious starting to come into focus: It's a trap all too many parents fall into.
These mindsets are then siezed upon by opportunists on both sides.
On the extremist left, the "WHITE PEOPLE AND MALES ARE RESPONSIBLE FOR ALL PROBLEMS" angle is the quintessential nadir of this mindset given wings. Since there's a big number of white people and a big number of males, they're essentially applying the same tactics of automatic guilt and shame-and-blame on a bigger scale, tapping into individuals who've already been victimized. And so, they come to believe that they're actually responsible and go to these out of a misplaced feeling of guilt despite having done nothing wrong.
The objective is to get you to surrender to authoritarianism by subjugating your own worth as a human being.
On the extremist right, this is taken in a different direction. Rather than internalized blame-and-shame, it's
externalized. Someone
else is wrong, but
you are the problem because you
tolerated their wrong-doing. The actual bogeyman used in the extremist right version tends to vary, with gays, other religions, and immigrants being the most common and exploitable targets. As the country as a whole has gotten more diverse and more accepting and intelligent, however, you might assume this mindset would be left to wither on the vine. You'd be wrong. Instead it simply finds new targets and the cycle repeats. They'll happily lock onto the actions of their extremist left counterparts to provide a description of
THE ENEMY, whilst at the same time guiding people towards an almost identical result.
The objective is to get you to surrender to authoritarianism by exploiting a desire to expel "undesirable" individuals from the stage.
Horseshoe Theory is quite real, as they say.
Not sure if sarcasm, or retarded 
