The article is right that accusation of racism are a conversation stopper in any but the most blatant examples of racist actions and speech, and even in calling those things out people will rationalize it away and say that don't really mean it the way people take it.
That's why even with proof that Donald Trump is a racist and has acted like a racist in the past, specifically to black people, people just rationalize it away and not take it serious.
Regardless, Donald Trump is clearly a bigot, CLEARLY, but it doesn't have the same weight behind the word and doesn't sound as provocative as calling someone a racist, which is why it's weird but I see people use racist interchangeably with bigot all the time, when something isn't even remotely "race" related. Bigot also is so broad in the scope of hate that even when you think that someone blatantly is a misogynist, racist, xenophobe, homophone, etc. and you call them a bigot, it just doesn't have the same weight as any of those individual terms.
Donald Trump is a bigot. It doesn't matter if he "really believes it" or not, he's run his campaign on those views and has fanned the flames of people who really believe those attitudes and live by them. He also hopes to enact policies that enforces systemic racism and oppression. Rationalize away his racism all you want, he is a bigot and that is a terrible quality for a person that is running for president. Someone who hopes to discriminate against citizens of this very country.