Evidence to whom? Not to me, because my evidence that he's deranged is that he's deranged. Not to the Republicans, because they love him and don't think he's deranged at all.
...from the Republicans. The Democrats go apeshit and think this is going to be the thing that totally gets him impeached you guys!
Who's Johnson? Gary Johnson? He was a Republican. He flamed out in the 2012 Republican primaries because he was a relatively sane Republican, and then ran as a Libertarian in 2012 and 2016.
You do have a point about Republicans acting unpresidential versus Democrats acting unpresidential. I really wish the Democrats would stop caring about that bullshit. If both sides are motivated by tribalism but Democrats think acting unpresidential is a bad thing, then acting unpresidential will rile up the Republican base and acting presidential will do nothing for the Democratic base. This is because the Republicans will love that the Democrats are outraged at their president, but the Democrats think acting presidential is just something a president is supposed to do. This shifts the payoff matrix from one where there's a perverse incentive to piss off the other side, to our familiar one where the Republicans are incentivized for behaving badly. Not saying either is a good or a bad thing, just a possible outcome.
The Republicans like fake outrage, good, let them be outraged. I bathe in Republican tears. Give them some real outrage to go with their fake outrage, some real fear (maybe 1/2 of what I feel day to day) to go with their fake fear. Cut out this "when they go low, we go high" bullshit. I can roll around in the mud with any Republican, and I like it easily as much as they do.
Besides, focusing on proper behavior is a distraction, and implies that we think decorum matters just as much as Terrorist Donny basically recruiting for ISIS and instigating a nuclear war with North Korea. I will gladly play a little dirty to keep all that mess from happening.