History has a lesson for Americans and that is that dictatorships are not difficult to create, all you need is to have people at odds with one another and for one side to get the upper hand. So, while all these moral arguments can be made about how Trump and his cohorts should be resoundingly impunned and punished "now or never", to do so now, would simply be accessing the current powers of one party over the other. That "breaks the dam" of democracy and the republic, things begin rolling downhill from there. America is and has been made "great" because it is a land governed by debate and persuasion, and not by the heavy hand of popular rule. A dictator may be popular and still be a dictator. So too, a president may be unpopular and still be president.
Pelosi is saying what the Republicans already know, a free country, and therefore their own positions, require that both sides come together or everyone fails. Remember the vote to strike down the filibuster? Did you note that the Republicans paid careful attention to the fact that they might very well need that rule, if they should be out of power? Well, eventually they will see that by not holding this President accountable, they might just as well forget about everything they stand for. Because once they create an imperial President, no one can stop insanity and the eventual carnage that will ensue. The Congress and the Courts all become mere "rubber stamps". That's what keeps the Courts from allowing unitarian rule. No matter how the courts are stacked, they realize that they must either jealously guard their own powers or become mere useless "rubber stamps". The same will happen to the Congress, but it takes both parties working together or it cannot be practically done. Not that it cannot be done, but that it cannot be done and have the desired effect of preserving the Democratic Republic. Thus they will all suffer a severe loss of power and status and practically everything else they've worked for as the regime changes for the worse.