Of course you're right that in general people must be held accountable for their crimes. However, it's somewhat different for children, who need and deserve some protection from the stupid things they do in their youth.
I fully support the punishment of the children, and any and all legal ramifications they receive, but I don't believe they should be help accountable forever. I suspect that when these kids go for jobs in 10 years, the first result in Google will be the post with their names and their foolish youthful actions.