Is it wrong to call Hitler a Fascist or Stalin a Communist?

if it's not wrong then how is it inappropriate for an ESPN reporter to call Trump a racist?

<snip>rac·ist/ˈrāsəst/
noun
noun: racist; plural noun: racists

1. a person who shows or feels discrimination or prejudice against people of other races, or who believes that a particular race is superior to another.
"the comments have led to him being called a racist"<snip.

Link;
https://www.google.com/search?source=hp&q=definition+of+racist&oq=definition+of+racist&gs_l=psy-ab.3..0l4.1157.10191.0.11772.22.21.1.0.0.0.186.2758.0j21.21.0....0...1.1.64.psy-ab..0.22.2784...46j0i131k1j0i46k1.Yys0mhx6Ghc