Two ways, 1. In our own communities, we should know at least a few who are 'on our side', but if you don't- 2. Ask.
For example, in my community, we have a Mexican Restaurant owned by a Legal Mexican Immigrant whom I've heard many a time complain about the protests and how these 'illegals' hurt legal Mexican immigrants like him because too often he is lumped in with them simply because of his nationality.
These are the type of folks we want to support.
Indeed we do.