... because after all, there is a huge body of evidence that says we should not believe him; he even lies about the weather.

https://www.thestar.com/news/world/uselection/2016/11/04/donald-trump-the-unauthorized-database-of-false-things.html#analysis

Note the above was published even before he was elected. The lies have been thick and fast since the election as well:

http://www.essence.com/news/politics/100-days-donald-trumps-lies-and-failed-promises