Except that these are not composed by illegal immigrants (actually the first favelas were created by 10.000 brazilian soldiers who were promised homes by the government if they fought in the "Canudos War" and, as usual, since the government did not keep their part of the deal, the soldiers occupied the place.)
Favelas, especially today, are the result of socialism and failed government policies(which are virtualy the same thing), not "illegal immigrantion".
Immigration is made illegal by the government(already a hint that it is a stupid thing, as almost anything that the government does, is). The REAL PROBLEM is the welfare state. And until republicans understand that and stop saying that the problems are "illegal aliens", as if they(americans) are somehow "better people" than the immigrants and the mere fact that they are "legal americans" makes them less prone to crime, drug usage and so on, they will continue to fuel the (false) narrative from democrats that they are "racist" and lose votes for it.
If the same americans were in the situation of these immigrants, they would act the same way and vice-versa.
I have an american friend, who voted for Trump in the last election and simply DESPISES THE DEMOCRATIC POLICIES AND IS CURRENTLY IN FAVOR OF CURBING ILLEGAL IMMIGRATION (just like I am, like I already stated in previous posts, even though I think it will always be a failed attempt to do so through government) and he's told me more than once: "If you ever go to Washington, take a look at the streets, you will see a great deal of homeless people. If you look closely, NOT ONE OF THEM IS AN IMMIGRANT, they are all americans. That's because immigrants, for the most part, come here to make a better life for themselves and are willing to do anything in order to get that(he himself is a soviet union refugee who has been in the U.S. for almost 3 decades and already is an american). But the americans are taking care of fucking that up through the welfare state(which fucks up even the intentions of these immigrants. After all, if, like many americans, they are able to get money with no work in return, many will).