"demonstrated" means someone proved it is false, not that no evidence has been put forth. Lack of evidence is not evidence.
That being said, my assertion was, quite simply, a comment that the state of America and politics tells me that Trump would get away with it.
"fake news"
"Lies"
"A plot to unseat a duely elected president"
"Self defense"
"Deep state faked the footage." <-This one is legit possible btw
Trump commands his followers with such ferocity that they'll swallow anything he gives them. And the local law enforcement, even the FBI would not have a process for arresting a sitting president. The DOJ, which is in the pockets of Trump, is not gonna change their position. And the senate MAY impeach him, I'm not sure it would actually stick.
THAT is how much Trump is loved by his followers. THAT is why I am afraid of Trump. He is half a brain away from being a dictator. His popularity is such that he could, if he played himself correct, take over America with "The Party of Trump".
Mark my words. If he lose in 2020, he will not give it up easily. He will fight to the bitter end and tell his supporters to do the same. If he wins, he'll tease (about half way through his second term) "So, what do ya think? Anthother 4 more years? Keep America great? I mean, who could do it better than me?"
So no, it has never been demonstrated that a sitting president can get away with Murder direct murder. They can with other kinds of murder, but that's all by proxy and military based.