To make a long story very short, each X-mas, I
work for an internet toy company by putting items
on Ebay.

Now, toys (for boys) = minors = very rude e-mails.

There are 3 things I do . . . 
1).  If they e-mail me through Ebay, I forward the
e-mails to Ebay for harassment claims or for SPAM,
threats, etc.  
2).  Don't EVER respond to any of those e-mails. 
The only thing it will do is let them know that
you exist and that you acknowledged what they said.
3).  Block them from bidding on your auction. 
They are obviously interested enough to e-mail
you, and usually it is because they can't afford
the prices and would rather see it sold for cheaper.

That is what I do and it has worked everytime.  :)