I am no fan of the Ayatollas but I fail to see the merit of dismissing the Mahdi as a “medieval holy man...”.
Please note that the belief in the 12th imams and his return by shia muslims is identical to the Jewish wait for the Messiah and Christians belief of Judgement day. So Netanyahu’s mocking of this core belief of shia muslims is hypocritical.
Such irreverence will only help to drive Shia around the world to extremists element of the Iranian clerical establishment and is totally counter productive to the security of Israel and regional and world peace.
References of apocalyptic wars are present in the Jewish bible and the new testament. That does not make mocking Judaism and Christianity a good idea.