There are lots of people RV'ing thru Central and South America. I have spent considerable time (months) in Venzuela, Bolivia, Ecuador Chile, Columbia and others.
Don't pay too much attention to those that tell you not to go.
There are literally millions of tourists every year traveling in every conceivable manner to all of the countries in SA. Many many people have driven the Alaska to Tip of SA (Tierra Del Fuego)in everything from campers to motorcycles.
Many of the roads are just fine. Most locals take their vacations by car. Services are readily available and generally very good (gas and hotels/campgrounds)
There are many Expedition sites and other sites on the web where you can read about peoples experiences.
Try Googling "Driving South America"
There are also at least two books written by those that have done this but the titles escape me...again go to amazon.com and search driving South America.
In general the people are extremely welcoming, friendly and like most other places are honest hard working people.
Just GO.