I believe throwing a chair into a large crowd will always start a fight because it may cause a massive chain reaction. When the initial chair is thrown, the person who gets hit may punch the person who threw it. Another person may think someone else threw the chair, and punch that person. Then they will punch each other back, other people will join in, throw more chairs, etc. A good example of this is the 2013 Carolina Awards fight.
There are a plethora of other reactions that can be stirred within a person in apropos to just aggression, like consternation, fear of being hit with the aforementioned chair. All individuals are not the same and thus won't always react with violence. And like the individual before me said, it really depends on what type of environment the chair is being thrown in.
While throwing an office chair into a crowd of anarchist is likely to provoke, throwing a bean-bag into a crowd a zombies might have no appreciable result. Even a loveseat, when catapulted at a crowd of jellyfish would probably start no fights. Throwing a hammock into a crowd of 420 activists actually just results in increased napping.
I have throw a chair into a large crowd many times. And only once has it ever caused any sort of reaction. Lawn mowers work much better than chairs if you're trying to get a reaction. I threw a lawn mower into a crowd, with the bar duct taped and still running, and wow. Everyone was running, and screaming. A few people came running towards me. But, I was already in my car. I guess people don't like it if you throw a lawn mower at the President.