Treat them the same as the rest of the non-Whites. Their behavior will be the same, if not worse. Mulattos like Malcolm X seem the most desperate to prove their blackness (in other words, act out childishly to prop up their self-esteem).
Your sympathy for their plight is very understandable, but realize that it is NOT a two-way street. And yes, it certainly is unfair. EVERYONE would be White if they'd been given the choice! But let me assure that no matter how diluted a Mexican's Indian blood becomes, he will still conduct himself in criminal fashion.