So, taking the allegory of the racial strife that the mutant strife puts a thin veneer on... Certain mutants cannot be denied. Mystique. Nightcrawler. Blink. Strong Guy. Etc, etc. Others can 'pass'. Those are only known by their identification and their association. It's for this reason, that sometimes humans are swept up in the 'mutie' hate - you don't hate them? You must be one! Just hiding amongst us! That's also one thing that stokes the 'red scare' type of environment that leads to Sentinels, mutant registration and mutant detectors.