I would be tempted to attempt to do something about it.
If I truly felt that this displayed a hateful and 'unbalanced' person who should not be around children, Then, the very last thing that I would be concerned about is this persons 'life' and their family!!!
If what you have found is as bad as you seem to indicate, then I agree that this is a real concern if this person is engaging in this activity on the school computer, on school time, when they are being paid to be working with children!!!
I would definately find out what the schools policy is on internet usage.
I would imagine that there is indeed a strict policy.
But, perhaps not?
As others have said, this could be a real gray area, unless what you have is truly objective (not subjective) in nature. I am thinking that this person is indeed crossing some lines (hate speach, etc...) The bottom line is, if somebody crosses legal lines, the the school can do something. If somebody posts something that you happen to disagree with, well, too bad....
I do have a question.
Your own credibility and motives here will definately be on the line.
Just how did you find out about this?
How are you sure you know exactly who is doing this? (could be just about anyone on that other keyboard???)
What reasons caused you to become involved?
I would give this careful consideration.
I would give a bit of time for the emotional shock and anger to pass.
Then, if you still feel you have concerns, then I think you should notify the Superintendant.