When you find a comment to be as objectionable as that one was, your best bet is to downvote it and flag it. You won't see the "flag" link when viewing the com

When you find a comment to be as objectionable as that one was, your best bet is to downvote it and flag it. You won't see the "flag" link when viewing the comment in the thread. Click the "nn minutes/hours ago" link and then you will find the flag option.