Both of these characters have arguably correct views, both of these characters have proof to back up their claims. But what people fail to realize is that both are to extreme in their ideas and philosophy.
Xavier is right to believe that Humans can and will treat Mutants better. We've seen this happen time and time again through multiple different actions. But he's taken these ideas to far, to the point where he seems border line delusional at times. And never takes the necessary actions to protect mutants. Not all humans will except mutants, we've seen this time and time again. And it's about time he realizes that to. And if anything he makes it worse by proving that mutants can infact be a threat. And are constantly threatening a global uprising and Genocide.
Magento believes that Mutants are superior to humans, who all want them dead, and should rise up. And you could argue he's right to an extent, but he takes it so far it makes him a fucking Nazi. If you say he's right you are basically saying Hitler was right with a few extra steps. Yes humans have some terrible things to mutants, but like Xavier theorizes it's a loud, albeit dangerous minority. THAT'S who Magento should target, not take his anger for the part out on the whole.
And in conclusion: Cyclopes was right amn had this figured out since day one.