You pose an interesting question. Yes it is true that there are more HIV infections in poor people that there are in rich. But as an epidemiologist I look at both numerators (how many infected) and denominators (out of how many). There are very many more poor people in India than rich persons so even if there were an exactly similar risk of infection, there would be many more poor persons infected than rich!
Another factor worth keeping in mind is that (sentinel) surveillance is carried out most frequently in sites in Government hospitals. Poor people tend to predominate there too, rich persons got to large corporate hospitals and so are not really included in the usual surveillance data.
Most HIV infection is through the sexual route (currently 86% in India) and the better off persons tend to use a higher class of contact than the poorer so are at lesser risk. Yes it also true that the rich people are more likely to be better aware of the risks of unprotected sex and to have access to protective devices such as condoms.
There is no evidence that well nourished persons are less susceptible to HIV. At least I have not come across reliable evidence to that effect. However there is evidence that better nourished persons take longer to succumb to HIV as their immune systems are less stressed and better.