Fallon was working from an old, outdated script, one that misses both the moral and the mortal threat of this year’s election. Twitter exploded with criticism of Fallon from the left, viewers furious that, by acting as if this election is like past elections, Fallon was normalizing Trump’s bigotry, xenophobia and lies.Fallon relies on there being room for we're-all-human-beings humor between the political parties. What he and his staff ignored is just how toxic Teh Donald is to a good half of the country (and I'm deeply saddened it's not a lot more). The people who reject Trump don't reject him as an ordinary politician: we reject him as a cancer on the body politic.
Any appearance that gives Trump free rein to charm without challenging him, goes this argument, establishes a false equivalence between Trump and previous Republican candidates—as well as between Trump and Clinton. Trump is not just another candidate and despite structural incentives to treat him as such, doing so has a moral valence, even if it is only intended to have entertainment value.
Fallon is the last guy in these fraught times who should tread anywhere near the intersection of politics and comedy. He comes off as a sycophantic tool, which kind of dents his aw-shucks nice guy persona.