ShiaPen’s published an article entitled: Ibn Taimiya’s open lie that the Hadith ‘he (Ali) is the guardian of every believer after me’ is a lie, falsely attributed to the Prophet (s)”, which can be found here.
ShiaPen, in this article, have provided the names and references to scholars that have authenticated this hadith. Their disagreement with Ibn Taymiyyah is sufficient for ShiaPen to brand him a liar. This action and accusation shows a lack of objectivity on the part of the ShiaPen team, for differences of opinions between scholars in the classification of reports in both the Sunni and Shia schools are immeasurable. To suggest that those that are mistaken are liars is a ridiculous proposition.
Regardless, in another article, in response to RevisitingtheSalaf.org, we have given the evidences and arguments in support of the view of Ibn Taymiyyah. That article can be found here.