Waters' language wasn't smart, but it wasn't an incitement to violence. It was an incitement to protest.The language got banned for using was even further from being an incitement to violence than that.
Trump held a rally within walking distance of the Capitol, on the day the votes were to be counted. He told the crowd the election was stolen and that they would stop this from happening. He told them to march to the capital (He did say peacefully, but he also said that he would march with them and did not). Some of his supporters went to the Capitol, there were violent confrontations with the police, pipe bombs were found, and windows were smashed to gain entry. Elected representatives were evacuated, their offices ransacked, and items stolen. The mob called for Mike Pence, the focus of some criticism in Trump's speech, to be hanged. Members of the press were attacked and had their equipment smashed (At the rally, Trump had called the media the enemy of the people and the country's biggest problem). Trump was reported as being pleased when the mob entered the Capitol, and initially refused to condemn the rioters, or even to tell them to leave.
Later, he tweeted his approval of his followers' actions with the following: “These are the things and events that happen when a sacred landslide election victory is so unceremoniously & viciously stripped away from great patriots who have been badly & unfairly treated for so long.” He added, “Go home with love & in peace. Remember this day forever!”
The Republican National Committee took a different view, strongly condemning the violence and saying that it did “not represent acts of patriotism, but an attack on our country and its founding principles.” Some republicans were momentarily shaken out of their complacency towards Trump's lawless rhetoric and called for stronger condemnation. Mitch McConnell said, "The mob was fed lies. They were provoked by the president and other powerful people," The next day, once a temporary twitter ban expired, Trump did condemn the violence and concede defeat. He later regretted conceding, and then tried to claim that it was Antifa that stormed the Capitol. This pretence that Antifa stormed the Capitol was taken up by some of the right wing media, and Republican politicians backtracked as Democrats tried to impeach the president and investigate the events of January 6.
Facebook and Twitter are private companies, they can do what they want. Their rationale for banning Trump might be easy to criticise, given their inaction on many of Trumps' previous posts promoting violence, but ultimately it was a commercial decision. Although sharing right-wing disinformation remains lucrative part of their business model, they may have decided that first quarter profitability could be affected if Trump's posts led to further violence or even government overthrow.