Trump thinks there are around 20 million mexicans in the US (illegal plus legal). The population of mexico is 120 million. So he thinks > 1 in 7 mexicans are rapists and murderers. Do you think that's close to the actual number?
The actual number coming in that he's calling rapists and murderers or the actual number of rapists and murderers coming in? In either case I don't find it relevant. He's not calling Mexicans in general rapists or murderers, nor is "Mexican" a race. What he's doing is speaking a conspiracy theory of how the Mexican government
is "not sending their best" as if the Mexican government is deciding who comes over the US border, and offloads its worst to the US. He's playing into his general anti-immigrant rhetoric. He's also doing that when talking about putting a "ban on Muslims from certain parts of the world until we know what the hell is going on". His shtick is that you don't know who is coming in and are not vetting people properly, so put a stop on it until you do. It is general paranoia and nationalism more than it is racism.
Trump's thunderous "Make America Great Again" and "Put America First" lines are part of the same rhetoric. He wants a more insular and self-serving America. This could be both good and bad for your country. I think you can expect to see a lot more anti-USA sentiment cropping up outside the US in the next few years and a lot of anti-rest-of-the-world sentiment cropping up within.