I think you're touching on a more general trend. People are waking up to the fact that punishments and jailtime are often excessive for criminals. And also that for too long people got away with saying terrible (but not illegal) shit. We're course correcting, but it does make for some strange comparisons. For instance, I would guess that many of the same people who pile on when someone's old tweets are found, (essentially ensuring that they lose/never get a good job again) would also be in favor of ban-the-box laws or donating money indiscriminately to bail funds.
Expunged... how? If you said some nasty stuff when you were 17, and now it's "expunged" because you turned 18, does that mean I can't say that that you did those things? Doesn't that violate my right to free speech?
Similar to "redlining" and other forms of discrimination. Expunged records can't be used to deny opportunity.
If the law is "once you're past 18 you can't be discriminated on the basis of what you said before turning 18", then it wouldn't have helped much for most of the students, since they were probably didn't turn 18 in between them saying the racist thing and the college discovering it. I guess you can reapply a year later, but that's already a year of your life wasted. Not to mention that there's nothing preventing the college from publicly rescinding the offer (unless that's also outlawed), and letting other colleges make some inferences. If the law is "you can't be discriminated on the basis of what you said under 18, including when you're under 18", then it would effectively outlaw admissions essays, which are literally designed to discriminate people on the basis of their speech. It'd also mean that you can be a racist all the way up to 18 with zero consequences, although you might we up for a rude awakening once you turned 18. This is as opposed to the juvie system, where you'd still get punished, but there's no records of it once you turned 18.