#1 - July 6, 2011, 10:10 p.m.
Simplyred, there are in-game filters that can be used to help remove content you'd rather not see. However, that doesn't make it any less against the rules. As long as you're reporting the offenders to the Game Master staff, they'll make sure appropriate actions are taken against those players. You can find the Harassment Policy here: http://us.blizzard.com/support/article.xml?locale=en_US&articleId=20455
Let us know if you have further questions.