He probably doesn't actually mean anything, personally. He's just saying something vague and inflammatory and letting people fill in the blanks by interpreting it in whatever way best aligns with their views (whether that means crime, drugs, economic instability, racial purity, or anything else). It's a fairly common strategy he uses, allowing him to maintain plausible deniability whenever anyone accuses him of being bigoted, while still telling bigoted followers exactly what they want to hear so they rally behind him and vote for/pay him.
This is my signature. It exists to keep people from skipping the last line of my posts.