You can report them by flagging the question for ♦ moderator attention. Since a year, they have the ability to remove questions from the Hot Network Questions list:
Moderators have the ability to remove questions from the HNQ List.
There are times when the hotness formula selects a question that a site would rather not have featured. Up until now, the only recourse that was available was to close the question (which may be appropriate anyway but isn't ideal when done purely to manage traffic), or to do nothing. We're putting the power in the hands of our moderators to remove questions that don't set a good example for their sites. I recommend each site have a meta discussion with guidance for moderators about when - if ever - a question should be removed.
Note that they might not immediately agree with you; you should use the flag message to convince them.