Hi Sasha,
We use "redeem" when someone has made a terrible mistake or something has gone very wrong, and amends are made so that hopefully, the damage is contained and others may see that person in a better light again. The person who has committed the mistake is also the one trying to salvage the situation, so we often use "redeem" with reflexive pronouns.
Examples:
He tried to redeem himself by paying for the losses.
They have redeemed themselves fully with a stellar performance.
Moving on to your sentence, violent video games are often seen as a cause of violent thoughts and behaviour in children who are addicted to them. In a sense, such games are seen as a culprit working against proper behaviour. However, someone has pointed out that children expend their energy through video games instead of acting out their frustrations in real life. From this perspective, such games actually help children to avoid using violence when they are off their game consoles, which is socially beneficial — these games which supposedly promote violence may turn out to help children in managing their behaviour instead — hence, we say that these violent games have "socially redeeming values".
Just as a side comment, "redeem" is used in many other contexts though not in yours. For example, we "redeem" a coupon or voucher for goods, discounts and services.
I hope this helps.