fas·cism | \ˈfa-ˌshi-zəm also ˈfa-ˌsi-\
Definition of fascism
1 often capitalized : a political philosophy, movement, or regime (such as that of the Fascisti) that exalts nation and often race above the individual and that stands for a centralized autocratic government headed by a dictatorial leader, severe economic and social regimentation, and forcible suppression of opposition
2 : a tendency toward or actual exercise of strong autocratic or dictatorial control
The people who think Donald Trump is a fascist generally do not know what they are talking about, because they cannot define fascism. They tend to accuse Trump of racism and then conflate racism and fascism. Alternatively, they call Trump a dictator and then conflate that with fascism. There is slim evidence he is either racist or dictatorial, and in any case, there is more to fascism than those two factors.
On the other hand, no one suspects the Regressive Left of being fascist because fascism has historically been considered a right-wing phenomenon, a perception reinforced by leftist rhetoric. Is this a false perspective? Are there possibly stealth fascists lurking on the Left?