It was not one poorly worded statement. He repeated it several times. His VP repeated it. His whole campaign was built around scapegoating Mexicans. He didn't mean that "some" rapists are crossing the border. He meant that generically the Mexicans crossing the border are rapists, but "some" are good people. This is textbook hate speech: insulting and inspiring hatred against a national group.
As for all that raping, the report says that
Rape can be perpetrated by anyone along the way, including guides, fellow migrants, bandits or government officials, according to Fusion. Sometimes sex is used as a form of payment, when women and girls don’t have money to pay bribes.
So no Mexican immigrants doing raping (note that the report is talking about Central American immigrants, not Mexican immigrants. Even then, I'd bet that most of the raping is done by corrupt policemen, not fellow migrants). Of course, you are not going to let mere facts change your opinion that Mexicans are rapists, are you?
And if you are genuinely concerned about stopping the raping, as opposed to just insulting Mexicans, I have bad news for you. Trump has no intention of actually building a wall. He knows it is a stupid idea. An unwatched wall doesn't stop anyone. And the manpower that would be required to watch the whole US-Mexico border is just insane. And even the mosted watched border in the world, the one between Israel and Palestine, has tunnels being dug beneath it every now and then.
Do you want to know a simple way to stop all that raping overnight? Open the border. No more people smugglers, no more corrupt policemen, no more vulnerable people alone in the desert.