The racist in America from the right and the left don't require any encouragement. There are racist that like Trumps immigration policies because they slow immigration from areas that have low skilled and low educated workers and encourage immigration from regions that have high skilled and high educations. While Trumps purpose in this is to improve the work force in order to fill the high level jobs that remain unfilled, it has a side effect of lower immigration influx of people with dark skin colors and their are racist that support the same policies for that reason.
Trumps border security platform has the intention of stemming the flow of drugs, human trafficking, and gang traffic, but also has a side effect of lowering the influx of darker skinned Hispanics, which again most racist support.
While the purpose of these two policies (the most controversial of his policies) is to enhance our workforce and safety and that is a laudable aspiration, the side effect of less dark skinned persons is not a consideration for him as it is irrelevant to anyone that is not a racist. He cannot do anything about people who chose to support his policy for the wrong reasons.