One of the problems is that the first Nigerians to come places like India are usually the drug dealers and gangsters, then the students, workers and businessmen follow. The Nigerians have been involved in organized crime in Mumbai since at least the 80's. So that combined with the general opinion of black people from American movies, the colour discrimination inherent in India and 19th century racial theories left by the British, shyt drummed by the media/politicians that 'outsiders' have been causing trouble etc. all come together to make Indians treat Nigerians and other Africans like crap. Similar story in Pakistan - the Nigerians have been running drugs from here for a while, so any poor African chap's luggage is thoroughly inspected, even if he's there only to buy textiles or second hand clothing.
As for Indians in Africa, they were brought in initially by whites (so they have that stamp of approval), they brought in and built businesses over time, which has a direct and indirect positive impact on the economy, even if they're racist as fukk and keep to them selves. Hence, Africans don't have a huge problem, but Indian mid-level labour is direct competition, especially in places like Nigeria.