The UN doesn't have its own military force. What you meant to say was "This is what members of various militaries really do."
In fact, as the articles point out, the UN is hamstrung when these events occur since it has no authority to discipline soldiers from the member nations. If you're upset that Sri Lankan soldiers acting as UN Peacekeepers committed sexual assault, your complaint should be with the Sri Lankan military. Putting on a blue helmet didn't magically change them into rapists.
Yes, that's the point, it's an obsolete organization, it organizes and starts stuff it can't actually handle. The EU wants to start up an Armed forces of its own, let them handle this, they seem to think they have everything figured out.
From first link:
And, in this case, Sri Lanka did; 114 of those soldiers were sent home. But what happened after that is anybody’s guess. There is no accountability. There are no names of any of these people, and nobody ever went to jail.
So, if you can imagine, these kinds of corroborated crimes against children over a three-year period, corroborated by a U.N. investigative team, and then nothing happens.