I don't see how this is difficult.
Trump telling those ladies to go back to where they came from, at the bare minimum, appears to be race based. Given his history, I don't see how it's defendable.
Now if he had said, "if they don't like things here, they may choose to leave" that's totally different. But he didn't say that.
I don't agree with much of what those ladies say, but they have the right to say it, and I will fight for that. They are American citizens, voted into positions of power by American citizens, and they don't deserve to be told to go back to where they came from. I also think that's part of the argument for why America is still a country where anybody can succeed. Illhan was an asylum refugee, became a citizen at 17, and eventually elected to Congress! That's pretty amazing!