About the iconography, our flag, etc. I agree with you, but if you use them it is very important to be clear and specific in whatever else the poster says, because vague statements can be very easily misread and those symbols by themselves will likely give comfort/anxiety to the wrong people. You can't just wave an American flag and say "resist fascism" or "preserve women's rights" or "protect children" or something like that, because those phrases mean different things to different people, and the color of the flag has been a useful way to know at a glance what the speaker intends.
From what I can see in conversations with Trump voters, it's the specifics that give them pause -- did I really vote for that? So, pick some particular action to respond to, or several in separate posters. There are so many to choose from.
Here is the quote, I had to click through a couple links to get to it, really they need to be putting his quotes front and center because by paraphrasing they make him sound more nuanced and reasonable than he is.