You must have missed the part about where I was referring to when they PM you. That means Private Message you. There is nothing to challenge unless and until they post the message as a public message. You don't need to waste your time if they only PM you, as my public message so stated.
Also, if you post their garbage post that they did not even yet post, you give their post (previously unposted, now posted in your response) credibility by posting your response to a post they have yet to post. Again, best to not respond publicly to it until they post it themselves.