You should report the comment or question or response. Underneath it there should be blue words that say "report as" with a gray drop down arrow and then you choose from different things such as offensive, spam, threatening, off-topic, nonsense, spelling/grammar, community standards, or offensive username. Then the mods will be alerted of this and will decide whether or not to take it down.
If it continues and you feel it crosses the line please reach out to customer service at: http://asksupport.custhelp.com/app/ask. Give them the details of what has been going on and they will be able to help you and alleviate the problem.