Senator John Mccain passed on less than 24 hours ago and president Donald Trump tweeted a condolence message but Americans are bashing him hard over the tweet.
Senator Mccain served in the military before joining politics and served for about 35 long years as a politician. He was captured for 6 years as a prisoner of war during the vietnam war. He also contested as the republican candidate in 2008 US presidential election but lost to Barack Obama.
Even though he was a republican like Trump he disagreed with many of Trump's policies and criticised him constantly and many Americans regard him as a hero. It's even rumoured that president Trump wouldn't invited to his burial.

Read some of the tweets below and there are many more on his page.

as much as Trump is a donkey, disliked Mc Cain and was forbidden (by Mc cain himself) to attend his burial, i see nothing wrong with Trump's respectful tweet.