You know, even when I was a kid I thought Magneto's plan in the first X-Men movie to turn everyone into mutants was fucking baller and they should have let him do it. Just 'cause that one guy turned into a water monster doesn't mean that would be the default - the X gene expresses way differently in everyone who has it.
An no, I don't think giving every human the X gene constitutes genocide, that's fucking stupid.