On behalf of Trump hitting that nuke instead of the nurse button.
Of course that is not how it works in real life. But. The dangerous play with war starts way, WAY before that. Badly chosen words, big egos by world leaders, all that can lead to a situation were war is one possible outcome. The more power is concentrated on a single person, the more real this danger becomes.
But even so, if the american president acts like a dick in front of other world leader, even IF consequences are not immidiate nuclear retaliation, the consequences can be severe. Economical, diplomatic, even lead to a new cold war.
If the president says stupid things, the other leaders and institutions of the US can also not just tell the world that these words have no meaning. its the effing president who dropped these verbal bombs. Best we get will be a "he didn't mean it like that".
One of the great things about Obama was that he was a natural speaker. A really talented one. And his speeches often were well written and thought out. Might be that Trump now tells his ghostwriters to change gears and write less "edgy" speeches for him. I fear he still lacks the talent, and cool head when it comes to handle delicate situations in his speeches.
If someone still fears the sky is falling, MOST probably he/she is less afraid of Trump, which at least changed his verbal gears. And most probably will NOT do much on his own due to is inexpierience.
What these persons are afraid of is most probably the people Trump will surround himself with. We have Pence, which seems to be a hardcore christian and very rightwing politician. There is Bannon, which seems to be rather a very rightwing news site chairman than someone with a political expierience.
Sure, these are just 2 names of 4000 he has to replace. But depending on his other decisions, this might turn out to be a horror cabinet for minority and more liberal people. They might not do much harm without the senat, where more traditional republican politicians still are the majority. But it could mean that even if Trump now changes his rethorics, other could keep feeding the fire with hate speeches. Trump could delegate that to someone who isn't the president.
Then there is the right extremist mob among the Trump followers. He got them out on the streets and in the mood. They will now not just say "oh, Trump didn't mean it like that, well then, lets put those KKK-hats back into the drawer". They are feeling empowered. And they are NOT controlled by Trump, if anything, it could be the other way.
Try to make it sound like its all fake news, and people being paranoid. The fear is real, and the reason for it grounded in facts. Even if the news would be fake, doesn't make the fact that people are getting more openly racist and sexist now that Trump made this a "thing" untrue.