Denial of the coming of Mahdi is his sign of appearance

Excerpt from Mr. Adnan Oktar's Live Conversation on A9TV dated March 24th, 2017

ADNAN OKTAR: What does God say in the Quran regarding our Prophet (saas)? "Those We have given the Book recognize it as they recognize their own sons." What does this mean? It means that God gave so many signs that they immediately recognize a prophet when they see him. So, prophets are not recognized through dreams, but how? By means of their signs. How will people recognize the Mahdi? By means of his signs. For example, some say that Mahdi will never come, which is another one of his signs. In sermons all across Turkey, it is preached that Mahdi will never come, which is another sign of his appearance. This is a great miracle.