President Donald Trump took to Twitter Thursday morning to attack former Vice President Joe Biden, declaring that “he is weak, both mentally and physically…he doesn’t know me, but he would go down fast and hard, crying all the way…”

Setting aside the reality of a one-on-one cage match between septuagenarians, what stood out to me was Trump’s use of “weak” and “crying.” It was a stark reminder of how trapped Trump is in within his arcane mindset that the only emotions worth showing — if you are a “real man” — are bravado and machismo.

I always thought one of the most powerful memories of President Barack Obama’s presidency was at the end, when Obama surprised his vice president with the Presidential Medal of Freedom. Biden was understandably emotional during this remarkable display of friendship, loyalty and respect. Juxtapose that to the time when Trump launched callous attacks against Myeshia Johnson, a Gold Star widow.

Crazy Joe Biden is trying to act like a tough guy. Actually, he is weak, both mentally and physically, and yet he threatens me, for the second time, with physical assault. He doesn’t know me, but he would go down fast and hard, crying all the way. Don’t threaten people Joe! — Donald J. Trump (@realDonaldTrump) March 22, 2018

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In one instance, we have Biden feeling free to express his feelings of gratitude. In the other, we have the president of the United States callously trampling on the feelings of the wife of a fallen soldier. Trump might not have cried when speaking with Johnson, but nothing about that interaction was strong.

Clearly, Trump thinks crying is inherently weak, and any emotion that isn’t anger or aggression isn’t an emotion men should show. His obsession with using nicknames like “little” or “crying” to refer to his detractors further illustrates this central tenant of his existence.

Of course the irony here is that Trump was emotional throughout the campaign trail. But while Biden’s emotional moments often seem to spring from a place of empathy, Trump’s emotions are mostly grounded in his desire to dominate and belittle. It is a true blind spot for Trump, and one which has been all too apparent during recent presidential moments. (Remember the cue cards Trump carried while meeting with gun-violence victims?)

Trump thinks crying is inherently weak. His obsession with using nicknames like “little” or “crying” to refer to his detractors further illustrates this central tenant.

Does anybody doubt how a President Joe Biden would have addressed the survivors and students of the mass shooting at Parkland High School? After watching Biden very publicly grieve for the death of his son, does anyone question how Biden would have approached a phone call with a grieving Gold Star widow?

If Trump’s first year in office has taught us anything, it’s that voters respond to genuine emotion and authenticity. Biden’s humanity, while a target for mockery by Trump (and sometimes others), is probably his greatest asset. And the notion that crying is a demonstration of weakness underscores why Trump has struggled with the (important) role of empathizer-in-chief during times of tragedy.

Presidents must be able to provide all different kinds of leadership. In times of strength, they must stand strong and tall. But they must also be able to model emotional maturity; to show us that we are strongest when we are able to grieve together — even when tragedy does not touch us directly. It is in these expressions of empathy and shared grief that we truly become united as a nation, bound together by our collective empathy.

Presidents must be able to model emotional maturity; to show us that we are strongest when we are able to grieve together.

Today, we instead are lead by a president who tosses paper towels to the survivors of a devastating Hurricane. He praises the “very fine people” on “both sides” of a white supremacist march. He refuses to talk about gun control in the wake of the worst mass shooting in U.S. history.

Of course, in 2018 it’s astounding that we are even talking about gender stereotypes at all. The idea that there is one way that “real men” should or shouldn’t act has been thoroughly debunked and the consequences so thoroughly detailed. Indeed, such stereotypes informed the attitudes of many of the so-called “real men” recently exposed by the #MeToo and #TimesUp movements.

When a bully picks on our children or siblings, we tell them that bullies lash out when they are confronted by their insecurities and feel threatened. Donald Trump is a bully. He doesn’t have the ability to demonstrate empathy or decency and so he makes fun of anyone who dares to express it themselves. Trump sees Biden as a threat not because of what he says, but because of what he can do — and what Trump knows he cannot.

Kurt Bardella is an NBC News THINK Contributor. He is a former spokesperson & Senior Advisor for the Chairman of the House Oversight & Government Reform Committee Rep. Darrell Issa (R-CA).Follow him on Twitter: @kurtbardella.