It's not just about the tweet though, rather how the party have been running elections for many years now. Obama being elected twice covered over a lot of gaping cracks in Democratic strategy. In reality they have been getting absolutely hammered across the country, losing record numbers of state seats, governorships and so on. It's gotten so bad that the GOP are extremely close to having the power to call a constitutional convention, something that was thought to be basically impossible at one stage.
Luckily, thanks to the orange moron in the white house and the rise of the Sanders movement, the damage is starting to be undone by a new focus on economic issues and grassroots politics. The big fear however is that the people running the national party will insist on their identity politics focus and piss away the gains that are being made. There are a serious number of high profile Democrats who seem to genuinely believe that they will inevitably win total power purely based on demographic change and on being morally right. It's a horribly dangerous position to hold.