Ignore them?
That may be a mistake.  We live in a country where everybody gets a vote..........appears to me that those many millions may be voting against your interests so it might be wiser to listen and know your enemy and try to fix the problem.
I watched them and listened to their interviews on tv.
They were mostly normal people, not paid shills and fools.
They were not violent, a fact that embarrassed Trump supporters who had predicted violence.
They articulated their concerns clearly and intelligently and were concerned about Trump's obvious attempts to abuse presidential power (thus the No Kings thing).
Sure, there were some kooks there like all demonstrations but they were a small percentage.
What struck me was the size of those huge crowds.........those people VOTE.
Trump's highly unusual actions in firing many thousands of political enemies without cause, arresting and jailing even children without due process, pardoning obvious criminals because they're Republicans..........and worse, his current tactic of pretending that all the people who disagree with him are terrorists who hate America........
These things are extreme and are obviously causing a huge backlash against Republicans.
When we hunt we have learned that the most important thing is to be aware of the direction of the wind.
Ponder these winds.