It has nothing to do with race and everything to do with the fact he is supporting vigilantism.  Regardless of what one thinks of the war on drugs, it is important to have due process.  Vigilantism means that Duterte can accuse any of his opponents as being drug dealers to banish them like he is with Senator del Lima.  Yes he is well liked, but that has more to do with the fact in the Philippines almost every recent president has been charged for corruption and poverty is really bad, so when things are going bad people are more likely to support radical leaders than when things are going well.