...and cause violence there! Recently, there was almost a riot in our university because of Afghan students (though Indians were also involved!) A student's car brushed slightly against an Afghan student and some 10 of them beat him up. Then Afghans were beaten. In reply, they were planning to beat down every Indian student in our hostel. However, this turned into a riot and both groups (200+ Indians and 50+ Afghans)…
On another, lighter note, riots add sort of a romantic tinge to college life. Hell, what's that UG in India where you didn't pelted stones against police or at director's bungalow(in our case the latter was the favourite and easy target, it didn't hit back).
Jokes aside, you have not mentioned the actual/precise events. What usually happens is a guy brushes someone(it might have been a knock and you might as well have downplayed it too) and then starts abusing the pedestrian itself, the guy who was knocked down. Now, if some friends were around then this called for a beating. Most probably this was the case.
BTW, Nigerian students sell drugs in Bangalore(mentioned city name because I live here and I know this from 1st hand exp from a safe distance or rather 2nd hand experience). But that doesn't mean all Nigerian students in India are into drug peddling and people from other countries are not. Most of this business is controlled by Indians though. It's rising alarmingly, subtly and almost without a check.
I am from a NIT. So, I knew many foreign students - mostly from Africa and Middle East. They were fun. Our favourite topic of discussion used to be girls in either countries, their sexuality and preferences and they were bloody curious why it's a taboo in India(esp people from non-ME countries). Among many things we almost generally agreed upon fcuk the religion. Yes, that included people from that religion too :-)
I had an Afghan friend(from another college, non-tech, we met at a fest). He was 6+ tall, incredibly handsome(one of my friends - I was sort of seeing her at the time - casually mentioned whether I could introduce them(2 girls) to him, I wisely diverted the topic), peace loving, god fearing and a thorough gentleman! Last month he told me, from EU(he moved there), that he got married and also lost his virginity. I was ROFLing for few minutes, he had typed both events in same line. I was not able to convince him in India to take the plunge.
Moral of the story, they(foreigners) are almost like us and sometimes I think better. You should not stereotype people. People like you ought to be stoned to fever!