There's something to be said for tradition, decorum and a sense of dignity. Here are some excerpts from an op-ed in The Hill written by Georgetown University Law Professor Jonathan Turley.
First, Pelosi dropped the traditional greeting before the start of the address, “Members of Congress, I have the high privilege and distinct honor of presenting to you the president of the United States.” Instead, she simply announced, “Members of Congress, the president of the United States.” It was extremely petty and profoundly inappropriate. Putting aside the fact that this is not her tradition, but that of the House, it is no excuse to note that the president was impeached. . . . .
Pelosi has demolished decades of tradition with this poorly considered moment. Of course, many will celebrate her conduct and be thrilled by the insult to Trump. However, even those of us who disagree with his policies should consider what Pelosi destroyed in her moment of rage. She shredded the pretense of governing with civility and dignity in the House. Notably, she did not wait to rip up her copy of the speech until after she left the House floor. Pelosi wanted to do it in front of the cameras, at the end of the address with the president still in the chamber.
That act was more important to Pelosi than preserving the tradition of her office. In doing so, she forfeited the right to occupy that office. If Pelosi cannot maintain the dignity and neutrality of her office at the State of the Union, she should resign as the speaker of the House of Representatives.