These are social spaces where a lot of young people essentially grew up. An important part of social development is making mistakes and learning from them. How can you make mistakes when those mistakes are archived for all time for everyone to see?
Similarly, we have a huge problem right now with massive partisanship in the west. Changing one's opinion should be viewed in a positive light, but unfortunately our society doesn't seem to see it that way. Someone with an odious opinion when they were young, who changes that opinion to something more moderate when they grow up, should be viewed as a positive change. But increasingly what we're seeing is people going through data sets to find those old odious opinions of somebody when they were 14 years old and using that as proof that they must still be a terrible person at 24. It's a paranoid, completely self-defeating worldview, but unfortunately it's all too common right now, and I think it's honestly a huge reason for the massive political polarization we're seeing in the moment.
So yes, shame on these researchers. I know they claim to have anonymized the data set, but let's be honest, that never works. It's always easy to find common threads and identify someone, and it's particularly easy now when we have access to all sorts of machine learning models that can really do very effective denonymization.