On an economic level the people that dislike it the most are the middle class Mexicans that are getting priced out of their neighborhoods by Americans. It really is an issue that you don't have to be that rich in Mexico to live a comfortable middle-class lifestyle, but "not that rich" (30k-40k pesos a month)means barely above minimum wage in the US. So tech workers and remote workers have began to move in because it's economically convenient to them and they can VISA hop right back home after their 6 months are up, or, if they actually buy property as Ralph (I think?) has done, they can just stay here forever (Mexicans can do the same in the US, by the way, it's an old NAFTA provision that I believe is still in the new FTA we signed) as residents (but as residents they at least pay taxes for the services they use and don't rise up the rents). So, essentially, people don't like a high influx of Americans coming in with their San Francisco salaries because landlords and businesses get wise to that and rise prices in the area, ultimately pricing out locals and building a little colony of remote workers.
On a social level, Americans are specifically disliked because they (being the remote workers, don't think it's fair to generalize to all Americans, or even all Americans in Mexico, which are plenty even without the remote workers) have a prepotent attitude, they frequently look down upon us, and they seem to believe themselves to be inherently superior to everyone around them, all whilst enjoying the public services of the cities they live in (which, as they live in middle to upper-middle class neighborhoods, tend to be pretty good) and paying no taxes. We've always had plenty of immigrants from rich countries but American remote workers specifically are far more unpopular than, say, Europeans or other Latin Americans. Lower-income economic immigrants (Central Americans and Venezuelans, with a slight dash of Argentinian waiters running from their inflation-death-spiral) are seen in the same sort of light as in the US: Poor, less educated than the locals, here to take dem jerbs, etc etc.
As for the sex offender registry, it's a very new thing in Mexico, and it's also not federal, let alone international. People would obviously very much dislike to have Ralph's presence around them, whether they knew or not he's a sex offender, but it's unlikely anyone would find out if people are not talking about it in their neighborhood or school. From what I gathered, Ralph's pretty insular in the places he lives in, and that generally just marks him as just a fat fuck with a horse, not much beyond that.
